It is appropriate that a memorial exhibition to the painter Michael Andrews should be held at the Timothy Taylor Gallery in Bruton Place, as it was in the building that Andrews had his first solo show exactly 40 years ago, in the days when it belonged to Helen Lessore's Beaux Arts Gallery. It's a small exhibition - just three large paintings and a small oil sketch - but a powerful one and not a little moving.

These were the last pictures that Andrews painted before cancer claimed his life on 19 July, 1995, pictures painted by a man who knew that they were his last and who told his doctor as the cancer spread: "I'm just thinking of finishing the next two pictures." The third of these large paintings wasn't finished, at least not in the conventional sense, but it's a terrific image nonetheless: a river of green paint dripping and splashing down the canvas, studded with flecks of grass and hay. It's an abstract image on a figurative subject - The Source of the Thames - inspired by his visits to the field in Gloucestershire where the river begins its journey.

The theme of these three paintings - the life of a river, the three ages of man - has a kind of epic, almost symbolic quality which fits with their being his last, though his friends, including the critic William Feaver (who has written an eloquent and touching memoir to accompany this exhibition) recall that the river entered his mind as a subject soon after he moved back to London from Norfolk in 1992, long before the illness took hold.

There are precedents for the river as a subject, in particular Whistler, who could almost have painted the little oil sketch at the entrance of the exhibition, and Turner, especially Turner, who used to sit in the vestry of Old St Mary's, Battersea, sketching the clouds as they scudded overhead. Turner's chair is in the chancel to this day and in his last weeks, Andrews would sit there, too. It's a poignant thought; indeed, it's a very poignant exhibition.

Michael Andrews, The Thames Paintings, Timothy Taylor Gallery, 1 Bruton Place, London W1 (0171-409 3344) to 20 June