Up a narrow street in Belem, Lisbon, and just yards away from the hungry tourists queuing for their Pasteis de Nata (the custard tarts which are a Lisbon speciality)  there is a chapel which re-opened as a gallery in September this year. Its outer wall has been transfomed by an art installation inspired by wood type. Chunky sans serif lettering of differing heights and depths has been applied to the wall and then given a coating of bright white render. The bold capitals are stacked into arrangements vaguely reminiscent of Henrik Werkmann.

The Chapel of the Immaculate Conception was dedicated in 1707. Unlike much of central Lisbon, it survived the catastrophic earthquake of 1755. The messages which now cover much of the outer wall are mostly religious, and more rigidly arranged than Werkmann's anarchic experiments. The piece is called 'Vai com Deus' (Go with God) and is the work of Oporto studio R2 Design.

It must have been a nightmare to specify and install. The letters have been individually pinned to the wall and are not always spaced or aligned with the kind of perfection we are used to. Perhaps this is why it has yet to feature on the web site of the award winning designers.

Last Sunday we had breakfast at the Café Madeira beneath the viaduct beside the Albert Embankment. I tucked into smoked salmon and scambled egg on foccacia - a bargain at £3.50. Everybody else seemed to be Portuguese. Respectable, decent, hat-wearing folk chatted convivially beneath big wall-mounted LCD screens. A bakery next door turns out dozens of reasonably-priced and tasty-looking Portuguese specialities. Further down the viaduct there's a gay gym, some clubs and several bars, all part of 'Voho' the Vauxhall 'gay village'.

There's even art underneath the arches. Not far from the tourist disappointment that is the Lambeth Walk, the once grand Lambeth Ragged School has been sliced through by the railway. It was built by Henry Benjamin Hanbury Beaufoy FRS in 1851 as a memorial to his wife. Ragged Schools educated 'about 800 children' At the school's opening, Lord Ashley portentously declared that 'there is no reason whatever why Lambeth should not rescue itself from the present disgraceful opprobrium which attaches to it.'

The gallery was founded with high-minded ambition of the kind the ragged school's founder would recognise. It aims to “fill a niche between the institution, the commercial and the ‘alternative’”.  It isn't exactly welcoming from the outside. In trepidation we pushed the buzzer beside a blank door set into a high wall - but the people inside couldn't have been nicer or more friendly.

There was an unexpectedly warm welcome at nearby Southbank House too. You can't help being struck by the fabulous Victorian building in Black Prince Road, all ornamented terracotta and glazed tilework set into the window ledges. A frieze over the doorway is one clue to the office block's distinguished past. If you look up, some fading lettering spells out the name 'Doulton'. A smiling caretaker led us to a gallery of photos that tell the story of how John Doulton built a vast business at Lambeth starting from a £100 investment in 1815. The Doultons' fortune was first made in glazed earthenware sewer pipes which saved the city from epdiemics of disease. Doultons then went on to make the fine china that was much admired by Queen Victoria.

Don't know a grawlix from a plewd or an agitron from an indotherm? Finding words for the marks made by cartoonists is a funny business. A jokey article about the marks cartoonists make for things like movement, emotion and radiation is now the stuff of earnest research into the visual language of cartoons.

It seems to have started with American cartoonist Mort Walker who wrote a satirical article in 1964 called "Let's Get Down to Grawlixes," for the National Cartoonists Society. In 1980 he expanded it to a book The lexicon of comicana. In Mort Walker's Private Scrapbook he writes:

'I spoofed the tricks cartoonists used, like dust clouds when characters are running or lightbulbs over their heads when they get an idea... I spent many hours at the museum recording their "language". I created pseudoscientific names for each cartoon cliché, like the sweat marks cartoon characters radiate. I called them "plewds" after the God of rain "Joe Pluvius".'

The spoof didn't quite work (even though the words he invented are very funny), because people really wanted words for the marks cartoonists make. So here is a run-down, from Wikipedia:

• Plewds Flying sweat droplets that appear around a character's head when working hard or stressed.
• Briffits Clouds of dust that hang in the spot where a swiftly departing character or object was previously standing.
• Squeans Little starbursts or circles that signify intoxication, dizziness, or sickness.
• Emanata Lines drawn around the head to indicate shock or surprise.
• Grawlixes Typographical symbols standing for profanities, which appear in dialogue balloons in the place of actual dialogue.
• Indotherm Wavy, rising lines used to represent steam or heat on hot objects -- however, the same shape found over a hot apple pie or something else strong smelling is a wafteron.
• Agitrons Wiggly lines around an object that is shaking
• Blurgits, swalloops Curved lines preceding or trailing after a character's moving limbs
• Hites Horizontal straight lines trailing after something moving with great speed, or indicating reflectivity (puddle, glass, mirror). Likewise, up-hites would be lines above an object falling.
• Lucaflect A shiny spot on a surface of something
• Dites Diagonal, straight lines drawn across something flat, clear, and reflective, such as windows and mirrors.
• Solrads Radiating lines drawn from something luminous like a lightbulb or the sun.
• Vites Vertical straight lines indicating reflectivity (compare dites, hites)

It's funny in a Sellars & Yeatman kind of way (something else that deserves to be better known). Dash Shaw responded to the comic challenge with a great cartoon strip using the symbols and The Balloonist drew a booklet for cartoonists using some new symbols. Needless to say, the academically minded take it all very seriously. Neil Cohn just about gets the point. But only just:

'He also attaches a myriad of useless names to them, to the extant that you feel that his whole point for jargon is to be facetious (which it may well have been).'

See also an explanation of Kirby Dots (developed by Jack Kirby to show an energy explosion) and a site devoted to cataloguing onomatopoeia like 'kaboom' (apparently first used in The incredible hulk, vol 1, no. 229, 1978).

Ivo (or Yves or Ives) of Kermartin, the patron saint of lawyers and abandoned children, is said to have been commemorated with the inscription "St Ives was Breton/ A lawyer and not a thief/ Marvelous thing to the people." It's somehow reassuring to know that lawyers were mistrusted even in the 12th century, and that there was at least one that broke with convention.

However, that St Ives has nothing whatever to do with the Cornish town of St Ives, which is named after a notoriously tardy 5th century Irishwoman who literally missed the boat that was supposed to take her to Cornwall with her chums St Erth (patron saint of gardeners and electricians) and St Uny. St Ia gamely made her own way across the Atlantic in a coracle, an act of such monumental foolishness that the townsfolk of St Ives decided to name the place after her.

Cornish people still honour her when they say they'll do something "d'reckly" - meaning at some vague time in the future, when they feel like it. Two days in St Ives this April converted me (again) to the relaxed ways of the place. People take the trouble to say hello just because they saw you out walking the day before; the staff at the Barbara Hepworth Gallery are happy to chat; and even the man who sold me tea took extra trouble to make sure it was just so.

Hepworth picked up on it when she wrote "St Ives has absolutely enraptured me, not merely for its beauty, but the naturalness of life". She loved the sense of community as well as the:

"remarkable pagan landscape...which has a very deep effect on me, developing all my ideas about the relationship of the human figure in the landscape - sculpture in landscape and the essential quality of light"

In the mid 20th century these key ideas - about connection to the land, community, and light, drew dozens of artists to St Ives. Nicholson, Garbo, Frost, Heron and the patron saint of British pottery, Bernard Leach, were the most notable, but you don't have to be a painter to appreciate the light in St Ives. It has a remarkable clarity - a sharpness that dazzles. Spoil from tin-mining and powdered granite in the dazzling sand are the prosaic explanation.

That light, the fresh sea air, the art, and the friendliness of the locals make St Ives just perfect for a break away from it all. We watched the surfers, walked the coast, visited the Tate St Ives and stayed in the Ped'n Olva hotel, on a rocky promontory with wonderful views of Porthminister beach and the harbour. The train from the London and the Thames Valley takes around 6 hours and costs as little as £30 return, including a trip on one of the loveliest branch lines in the country.

A report in Pravda (of all reliable sources) says that centaurs were real. Researchers decided this because of the number of cave paintings depicting the chimeric creatures. The article states, in a somewhat old-fashioned translation, that:

"Historical sources reveal that buggery was very popular among ancient Greeks and Romans. A legend says that Greek scholar Thales recommended his master Periandr not to engage unmarried shepherds nor to produce more centaurs."

That interpretation may not convince, but there is no denying the creatures' pervasiveness. For 3,000 years or more the half-man, half-horse has been lodged in the collective consciousness, inspiring myth-making and art, standing both for animal passion and for the genial guardianship of knowledge.

The Centaur's Smile: The Human Animal in Early Greek Art  is the catalogue of a 2004 Princeton exhibition which charted examples from as early as 750BC. In Pindar's poem, the kindly centaur Chiron 'smiles greenly' (as if with secret knowledge) at Apollo when he seeks advice on seduction techniques.

Guido Reni (whose 'Rape of Dejanira' is above) is one of countless gay artists since who have been fascinated by beastly half men.

Bruce Rogers' beautiful typeface Centaur was first used in 1915 for an edition of de Guérin’s prose poem Le Centaure. The font was later issued in a commercial version developed by Rogers and the Monotype Corporation. In de Guérin's sensuous story, the aged centaur Chiron describes his early days to a young mortal who seeks him out on a mountain top.

Other interesting editions of the de Guérin story include one printed by Ricketts and Shannon at the Vale Press in 1899 and this art deco interpretation featuring a distinctly un-menacing centaur by George Barbier (1928). Ricketts returned again and again to the centaur theme. In 1902 the artist and his long time collaborator Shannon were the models for a small painting of Nessus and his stolen bride Dejanira in which:

"This bold defense of Nessus’ “rape” portrayed a willing Dejanira with strong shoulders, arms, and calves."*

Evidence that centaurs still hold a considerable homoerotic charge is provided by the recent phenomenon of 'boytaurs'. They are celebrated in a somewhat indecent website featuring 'Online resources for boytaurs, multilimbers, shapeshifters, and their friends'.

One lexicon defines a modern day centaur as "A gay man who lives openly in a predominantly heterosexual suburb."

“If you start to take Vienna - take Vienna” said Napoleon. A tall order for the art-lover with just four days in which to attempt to do justice to the major sites. The Kunsthistorisches, the Albertina, the Belvedere, the Imperial Library, the Ephesus and the Musical Instrument collections, the Hofburg, the Schönbrunn. The Cathedral, the Karlskirche or the Peterskirche? Canova, Dürer, Caravaggio or Vermeer? Baroque or Secession?

All the booty of empire gathered within the 4km ring, lined with palaces cascading with statuesque caryatids and writhing atlantes. Churches with walls coated with plaster angels forever tumbling into the inferno. A Haydn, Mozart, Beethoven or Strauss commemoration on every corner. And the cakes!

Vienna oozes history and its unconcerned citizens embody a favourite word of Queen Victoria's. They and their city are 'Gemütlichkeit' - contentedly belonging, polite and unhurried. On the plane a Viennese offered tips on getting the best from his home town. In the Graben, the city's busiest shopping street, half a dozen people stopped and waited while I pointed my camera up at a building across the street. At junctions cars halt and pedestrains are waved across. Gentlemen of a certain age wear hats. Their ladies are impeccably (and somewhat conservatively) dressed. Even the frock-coated touts for Strauss concerts are polite in their salesmanship.

We marvelled at the Prunksaal of the Imperial Library with its ravishing ceiling decorations and perfect proportions, justifying the claim that it is the finest library hall in Europe.

Mohr in Hemd (chocolate pudding) or Kokosbusserln (Coconut Kisses)? The cakes are as elegantly refined as the Viennese. We ate Sacher torte in a relaxed and splendidly old-fashioned café by the rear entrance of the Hofburg Palace. A Secession facade there so offended the emperor with its 'plainness' that he reputedly never passed it again. 

We resisted other temptations including the discrete entrance of the exotically Turkish Centralbad which was a haunt of the Archduke Ludwig Victor, a brother of the emperor Franz Josef I, who 'was famous for his love for beauty'.

We admired Canova's tomb for Maria Christina at the Augustinerkirche. It was such a success that Canova himself was buried in a copy in the Frari in Venice. In the Kunsthistorisches we ate more cake and lost hours in the galleries. Not one but three Rembrandt self-portraits. Exquisite Roman cameos and gold jewellery quite unlike anything I had ever seen. 

An incredibly myopic Jehovah's Witness seemed to be stalking us in the clock museum. All three floors are choc-a-bloc with chiming timepieces. He was a museum warden and seems to spend his days reading scripture, held at about 2" from his nose. In the museum of musical instruments (rooms of shawms, serpents and Beethoven and Chopin's pianos) another warden was nervously writing who knows what never to be published masterpiece on scraps he carried round with him.

Austrian Art Nouveau toyed with plainness but finally embraced ornament with relish. We admired Otto Wagner's Majolica House which is a riot of coloured tiles and ornamental balconies. The secession building has a glorious gilded dome of glittering laurel leaves. More pictures here.

Which are the world's 50 greatest works of art? The Telegraph has published Martin Gayford's list. It's necessarily a fabulously subjective exercise, running all the way from an Egyptian sculpture of 2800 BC via van Eyck, Michelangelo and Velázquez to a sculpture by Donald Judd from 1982.

I was pleased to see the haunting Pompeii 'Villa of Mysteries' frescoes included, together with Giotto's breathtaking Scrovegni Chapel in Padua and Constable's 'Salisbury Cathedral from the Meadows'. 

But no Sistine chapel, or Turner 'Rain, Wind and Speed'! The Mona Lisa is knocked off her perch in favour of the same painter's 'Lady with an ermine' in Krakow. What about David's 'Death of Marat' with its superb handling of paint and poignant mythologising of the French Revolution? None of Ingres' portraits, with their relentless scrutiny of subject and no Delacroix or immaculate Vermeer interior? And what about the searing intensity of El Greco - and the homespun passion of Stanley Spencer?

And are the terracotta army and the Easter Island statues art works in the same way as the Jackson Pollock is thought to be? (I would have replaced it with something by Mark Rothko). Both the Easter Island statues and the terracotta army seem to me to be functional objects, created to fulfill a specific purpose, quite different to the making of an art work for its own sake.

I counted a respectable eight or so I've seen, but (with the help of some carbon offsetting), there's clearly plenty more prime art waiting to be discovered.

What is the 'real meaning' of art and what value should be placed on what is 'authentic' over the work of copyists?

At Christ Church Picture Gallery, Oxford, Curator Jacqueline Thalmann provided a fascinating introduction to the collection which is housed in a striking subterranean gallery from 1968 by Powell and Moya.

Although best-known for its collection of old master prints and drawings, over 200 paintings were bequeathed in 1765 by alumnus General John Guise, whose somewhat robust taste includes a Martrydom of St Lawrence by Tintoretto and a large and gruesome 'Butcher's shop' by Annibale Carracci (1560-1609) which since it was judged unsuitable for the contemplation of women hung in the College's kitchens for some 200 years.

Before the Renaissance, the best religious icons were those that faithfully copied from precedent. The essence of the divine could only be transmitted by the careful replication of visual convention. Any notion of artistic originality was irrelevant.

By Dürer's time the artist, not the subject, was the focus. His work – including a prominent monogram – was faithfully copied by a highly talented printmaker called Marcantonio Raimondi. In 1511 Dürer issued a devastating warning to anyone tempted to infringe what he was effectively asserting as his copyright: "Hold! You crafty ones, strangers to work, and pilferers of other men’s brains. Think not rashly to lay your thievish hands upon my works. Beware! Know you not that I have a grant from the most glorious Emperor Maximillian, that not one throughout the imperial dominion shall be allowed to print or sell fictitious imitations of these engravings? Listen! And bear in mind that if you do so, through spite or through covetousness, not only will your goods be confiscated, but your bodies also placed in mortal danger."

In what must be one of the first cases of its kind, Dürer succeeded in getting an injunction against Raimondi banning him from ever again misusing Dürer's trademark.

In common with the Carracci 'Butcher's shop', Anthony Van Dyck's 'Continence of Scipio' was revealed to be rich in multiple meanings. Van Dyck gave the famous Africa-conquering general filmstar looks, painting him into an epic scene reminiscent of Cecil B De Mille. Scipio's bright red cape billows as he nobly rejects the woman offered him in tribute. Her face is downcast and classically impassive whilst her betrothed, hand on heart, gazes beseechingly deep into the General's eyes.

The work was commissioned from the young Van Dyck by his court champion the Duke of Buckingham, whose stone capital, carved with two male faces, frames the scene. But the connections with Buckingham run deeper – Scipio can be read as James I, and the beseeching figure as Buckingham himself – James' 'favourite' and lover.

According to some 'queer historians' at least, gayness is also to be discovered in Dürer's life and work, not least in the woodcut 'Men's Bath' which features a prominent monogram (and a rather suggestive tap). Dürer's lifelong friend was a bisexual humanist called Willibald Pirckheimer. The humanist sent the artist drawings of the two of them in flagrante together. Consumed with jealousy, Mrs Dürer accused her husband of having a sexual relationship with the anagrammatic Pirckheimer.

Web find of the month is a site devoted to complete reproductions of illuminated books. It includes Owen Jones' astonishing Grammar of Ornament (1856), a tour de force of nineteenth century letterpress and chromolithographic printing which has had an incalculable influence on artists and designers from the Art Nouveau to Gaudi in Barcelona.

Owen Jones' most influential book contains his own re-drawing on 'scientific' principles of over 2,000 decorative designs. The scope is vast: from designs created by 'savage tribes' to ornament from the ancient world, Arabia, China, India and Europe. The motifs presented range from intricate and highly elaborate high Renaissance manuscript illumination to apparently simple geometric tile designs from Moorish Spain and Persia.

A passion for the orient

Jones (1809-74) was an architect who became passionate about the superiority of non-European ornament after touring Turkey, Egypt, Sicily and Spain in 1831. Henry Cole, who founded the Victoria & Albert Museum, was one of his many collaborators.

Jones' passion for the near east found expression in his most significant work as an architect on the interior of Christ Church, Streatham. He was criticised for his  'excessive use' of Islamic motifs there.

Acclaimed for his decorations for the Great Exhibition in 1851, Jones worked for nine years on the publication of a lavish folio work, which exploited the capabilities of the relatively new and demanding process of chromolithography. He sold property to finance its publication, setting up his own press and training his own staff to produce it. He did not live to see it succeed commercially, and many copies were remaindered.

Besides including a historical survey and commentary on the many gorgeous full page colour illustrations, Jones developed a series of 37 'design propositions' which attempted to codify the construction of well-made ornament. For Jones: 'All ornament should be based on geometrical construction' And 'true beauty results from that repose which the mind feels when the eye, the intellect, and the affections, are satisfied from the absence of any want'. In his final chapter he advocated a new kind of architecture based on natural forms.

The rhythm of life

There is an enduring appeal in many of these stunning illustrations. They combine a remarkable and carefully constructed rhythmic intensity with a highly developed colour palette. Since the Modern Movement, architects and designers have associated ornament with the literally superficial, seeing it as a layer of irrelevant decoration that obscures the underlying nature of whatever it is applied to.

For me and I suspect for Jones, the desire to decorate is an integral part of human experience. His use of geometric reconstruction seems to link to metaphysical ideas of the golden section or 'divine proportion' which were taken up by Modern Movement architects such as Le Corbusier.

Good ornament is intrinsic to the very essence of things.

The Grammar of Ornament on CD-ROM for designers.

Seven paintings, all of the same subject: a beautiful, almost naked youth, tied to a tree, in the throes of martyrdom. Five are almost identical versions of the same composition, from galleries as far away as Puerto Rico and New Zealand. All are uncompromising in their directness. The painting from Genoa inspired Wilde, Mishima and Pierre & Gilles. Stendahl claimed they so distracted the faithful that they had to be removed from churches.

The St Sebastians of the 'divine Guido' Reni (1575-1642) feature in an exhibition at the Dulwich Picture Gallery until May 11. It offers the public the chance to play an intriguing game of art historical 'spot the difference'. Which are 'real', which are copies? How much is the work of the master, and how much of his studio? Why are they such gay icons?

The Rome painting lacks the impact of its Genoese neighbour. The paintwork is softer, the face and body less defined. A third arrow has pierced the martyr's side and the feathers of another don't now clash with the Roman soldier in the background.

Standing in front of Reni's version from Genoa it is easy to see why it had such impact on Wilde: an athlete of classical build is indifferent to his wounds. Sacred: his boyish, asexual face, framed by his pinioned arms, gazes heavenward. Profane: his loincloth slips provocatively, emphasised by a partly turned hip.

Pierre & Gilles and Jarman also responded to this sultry mix of agony and ecstasy. Yukio Mishima had himself photographed as St Sebastian and in Confessions of a Mask the narrator discovers his sexuality because of a print of the painting.

Of the six versions of the (earlier?) composition, that from New Zealand is the most obviously different. The brushwork is far looser, there is less light - yet in spite of these differences, the current view is that it is by Reni himself. Comparing the others on view, they all seem as one.

The Dulwich's own St Sebastian was long thought to be a copy of the painting in the Prado, Madrid. Now restoration has revealed signs of pentimenti (second thoughts) that have enabled its attribution as Reni's own work.

For one critic Reni was self-consciously re-working notions of light, texture and atmosphere, the repeated composition a means to an end. Perhaps the explanation for so many versions is more prosaic: Reni wanted cash and welcomed requests for repeat business. He certainly went on to make other paintings of this middle-aged Roman soldier, the parton saint of sufferers of the plague, who met his final end only after his wounded body was dragged out of the cloaca maxima. Either way this Dulwich exhibition (which deserved much greater space) is fascinating.

The exhibition is complemented by a catalogue which contains more art historical analysis than is usual. Also on show was 'The age of enlightenment: Beardsley, Dulac and their Contemporaries 1890-1930' - Beardsley's perfumed and obsessional exoticism providing another take on image making.

Comprehensive Survey of images of St Sebastian

Review in the Independent

You have until 13 January to see the Tate's latest blockbuster: a seven room survey of the entire career of Sir John Everett Millais (1829-96), perhaps best known for his Ophelia and 'Bubbles' the Pears soap boy.

The greatest painter of his day produced what was then regarded as his greatest painting in 1854-6. The blind girl is a colossally garish exercise in high Victorian sentimentality. Patronisingly, we are asked to sympathise with the poor blind girl, who is unable to appreciate the sudden brilliant sunshine and rainbow that decorates a lead-grey Winchelsea sky. The two girls are awkwardly plonked down on a stream bank and (like several other of his paintings of the time) seem about to separate from the background. The 'pathetic' scene is completed with an improbably applied butterfly on the blind girl's right arm (delicate beauty she will never appreciate) and a toybox collection of country creatures which is randomly strewn across the irridescent meadow behind them.

Isabella (1848-9) was Millais first painting as a member of the Pre-Raphaelite Brotherhood. It is both unsettling and unsatisfying. On the right a pink tunic wearing Lorenzo offers fruit to his Isabella, whilst a disapproving servant looks on. Lorenzo's face looks cut out and is curiously lit. On the left Millais casts some of his own friends, the affectionate reality of their portraits at odds with the fantasy scene across the table from them.

But it's not all bad. Millais was indisputedly an incredibly talented and highly precocious artist and draftsman. That we find his themed works not to our taste is perhaps because they were the soap operas of their day. We get these kicks from Eastenders and Corrie.

The Black Brunswicker (1859-60) is another exercise in popullist melodrama, only this time Millais has resoundingly pulled it off. On the eve of Waterloo a soldier departs to his death. Agonised, his wife tries to prevent his departure, her hand pushing the door closed as he opens it. As she gazes sadly at her imploring lapdog, an etching of Napoleon hangs behind them. The painting is quite sumptuous, the composition perfectly suited to its remorseless narrative. The work sold for 1,000 guineas and made Millais' reputation.

By 1864 Millais' style had evolved considerably. In 'Leisure Hours' (the quotation marks are the painter's) he has painted the Pender sisters as perfect ornaments, trapped in enforced idleness just as much as the goldfish in the bowl in front of them. The paintwork is a little looser and without distractions. The blank stares and suffocating stillness of the composition all add to the narrative, unlike some of his later portraits of women and children, which contrive to be either sickly sentimental or alienatingly haughty.

Painted at the same time, Esther (1863-5) shows brilliant mastery of the decorative use of colour coupled with an understated and elegant composition. Esther releases her hair as a gesture of defiance to entice a king. Compared with Whistler's full length female portraits and admired for its 'flashing whites' by Rossetti, this is a very satisfying work.

In his later period Millias painted some fine political portraits, inspired partly by Velasquez and Rembrandt. I was particularly taken with The Rt Hon. WE Gladstone, MP, (1878-9). Isolated of all props, Gladstone is austere, almost a visionary. With even looser brushwork and dramatic lighting, this is Millais at his most compelling.

In 1878 Millias was grief stricken at the death of his second son George Grey. He painted 'The tower of strength which stood Four-square to all the winds that blew'. – Tennyson as expiation and it makes an interesting comparison with Constable's Hadleigh Castle, on view at the RA and painted in similar circumstances. Urqhart Castle on Loch Ness is a Romantically ruin, dissolving in uncertain, smudgy paintwork. The overpowering sea and sky are thick with expressive paint, against which the heroic lone oarsman battles.

Millais' last works are an elegy to the Scots landscape. In them the painter achieves a kind of apotheosis.

An acquaintance (whose accent locates him in the mid-atlantic, but whose prejudices are decidedly continental) once said to me that 'nothing of world class is ever produced by British artists'.

We were on the steps of the Royal Academy at the time. One collector who would certainly have disagreed was Paul Mellon (1907-99) the pick of whose Yale Center for British Art is on tour to the RA until January 27, 2008.

Mellon got his money from his father, the third richest man in America, and his taste for British art from spending his earliest days in England. Christened in St George's Chapel, Windsor and educated at Cambridge, he bought his first major painting, Stubbs' 'Zebra' in 1960 for £20,000. So unfashionable was painting of Stubbs' era that it was sold in a bric à brac sale by Harrods.

This astonishing portrait of 'the queen's she-ass' pictures it in a pool of golden light in a lush imagined forest. The creature, newly arrived at Queen Charlotte's menagerie from South Africa, has the look of a miraculous mythical beast. St Eustace might appear at any moment.

Mellon's collecting was intuitive. He mistrusted art historical analysis and bought because a picture appealed, not because its narrative impressed. In a decade or so he assembled (and subsequently gave away) a collection that is a roll call of the greats of British art: Hilliard, Hogarth, Reynolds, Gainsborough, Turner, Constable, Blake, Wright of Derby, Landseer, Palmer, Zoffany and Dadd. All are magnificently represented in the RA show. In addition there are superb topographical artists like Paul Sandby, caricaturists like Rowlandson and names new to me like John 'Warwick' Smith (1749-1831), John Robert Cozens (1752-97) and William Turner of Oxford (1789-1862) whose 'Donati's Comet' is a surreal night-time view almost reminiscent of Magritte.

The star of the show is Turner's vast, dazzling 'Dort Packet Boat' (1818), described then as 'one of the most magnificent paintings ever exhibited'. Turner's mastery of light is triumphant.

Two smaller Turners are almost as stunning. 'Staffa, Fingal's Cave' (1832) was completed the same year as Mendelssohn's work. A grubby little steamer pitches in a storm beneath the sunlit splendour of Staffa's cliffs.

In his 'Eruption of Vesuvius', minute figures are panic-stricken on the shore, powerless against the great red fury of the volcano. 

Constable's 'Hadleigh Castle' (1829) is another blockbuster. From not very close up at all the 6 foot wide painting disintegrates into fractured, glittering brushwork. Constable's angry grief at his wife's death is painfully visible.

Mellon was not only a great collector of paintings – he was also one of the greatest book-collectors of the twentieth century. Works on show include Caxton's Canterbury Tales (perfect presswork, even at the very beginning of printing in England); the magnificent Kelmscott Press Works of Chaucer; and the only hand-coloured edition of Blake's gorgeous Jerusalem. In plate 99 an androgynous Jerusalem is clasped by Jehovah 'awaking into his bosom in the life of Immortality'.

Save for Burne Jones' collaboration with Morris, Mellon avoided artists associated with high Victorian excess. There's no sickly sentimentality here. Mellon's intuition was razor sharp - they may be unfashionable, but these are works of superb quality and refinement, in huge contrast to the masochistic indulgence of the Baselitzes on show on the floor below.