Who was the most dotty Modern British artist? And how come he was actually French? Find out at Sotheby's on Wednesday
You, too, can dress up as Rudolf Nureyev. Christie's has estimated the late, great ballet dancer's scuffed ballet slippers as low as pounds 100 a pair. Those stamped "Mr R. Nureyev" have premium value: pounds 1,000-pounds 1,500 is expected.

Costumes will cost you more at the two day sale, Monday-Tuesday (10.30am daily). The catalogue descriptions have a voluptuous flavour: for pounds 2,000- pounds 4,000 "a bolero of raspberry pink shot silk" from his Basilio in Don Quixote. Basilio's tunic of black figured silk with built-in orange silk underblouse is estimated pounds 3,000-pounds 5,000.

Just fancy, if Lucien Pissarro, son of the renowned French pointilliste painter, had stayed in France, his painting of his brother, estimated pounds 80,000-pounds 120,000 at Sotheby's on Wednesday (11am) might have had a tag of pounds 500,000.

As everyone knows, true pointillistes (painters of multi-coloured dots) were domiciled in France and were members of the foursome Seurat, Signac and Pissarro (pere et fils) that caused such consternation at the 1886 Impressionist Exhibition.

It was actually the 22-year-old Lucien who introduced his father Camille to Seurat, who had already started painting in little dots. But by 1890, with scant regard for tidy art market prejudices, young Lucien had abandoned dottiness and emigrated to Britain.

From then on he was regarded as a British artist, on both sides of the channel. His sparkling picture of his brother Georges, rediscovered and hitherto unpublished, appears in a Modern Brit sale, not an Impressionist sale. A second painting, of a garden path, painted in France in 1889 and with a hatching rather than dotting technique, anticipating his later style, is est pounds 25,000-pounds 35,000.

The Modern Brit market is going for safe names: Sickert, Bomberg. A run- of -the-mill Sickert is pounds 35,000-pounds 40,000. Lucien Pissarro is not a safe name. But he was a leading light in the Dotty Four, and, whatever his biographical eccentricities, his picture of his brother remains as vibrant as ever. Art snobs will miss a snip.

Other Modern Brit sales: Christie's, Tuesday (2pm), twinned with a dedicated Russell Flint sale (5pm). The two catalogues are joined by an ochre-coloured paper cummerbund, clearly for the preservation of modesty.

The market is absorbing the large number of bird watercolours thrust upon it - just. Sotheby's is holding a second annual bird picture sale, Wednesday (10.30am), in which estimates for a second bunch of de-acquisitioned bird pictures from the Glenbow Museum, Calgary, Canada has been adjusted downwards. The first bunch was in last year's sale, which raised pounds 493,000 with 36 per cent unsold. Also on Wednesday at Sotheby's (2.30pm): over 100 bird pictures by C F Tunnicliffe, being sold off by the RSPB. Few Canadians buy bird paintings. Thank goodness the British do.

Next week sees Sotheby's "The Book as Art" sale of modern illustrated books (Tuesday, 10.30am) and Christie's South Kensington's sale of optical toys (Thursday, 2pm). The estimates for the book sale are on a separate sheet - a hark-back to old times when one could read saleroom catalogues without being reminded of the distasteful subject of money.

For auctions nationwide, see pages 16 and 17.

John Windsor