Art: Private View - The Gere Collection The National Gallery, London WC2

The late John Gere, Keeper of Drawings at the British Museum and a distinguished art historian, was also an inspired collector of a very specific sort of painting. Over a period of about 40 years, he and his wife Charlotte amassed one of the finest private collections anywhere of landscape oil sketches - direct studies made en plein air usually on a small scale, often as a prelude to a "finished" painting.

"Plein Airism", as the name suggests, is often thought to be a French invention, and certainly the Impressionists made it their own, though as an artistic practice it is probably as old as painting itself. Until the Impressionists, however, these sketches were rarely intended for exhibition and so, with the exception of a few of the more famous examples, such as Corot's Italian sketches or Constable's cloud studies, they have often been missed out of the usual notes of art history.

The great joy of these little pictures is exactly the thing that has kept them in obscurity: an incidental, unimportant quality; the sense of a quiet moment or the effects of light or weather, caught fleetingly. These are private masterpieces made for personal consumption, rather than the public statements on which artistic reputations rise and fall, and they are all the more pleasurable for their lack of pretension.

The Gere Collection of Landscape Oil Sketches, The National Gallery, Trafalgar Square London WC2 (0171-747 2885) Wed to 30 August