The man who led a double life

VISUAL ARTS James Gunn Fine Art Society, London

It's a summer's evening, and a group of young men have left their tents to bathe in the clear water of a French river. But the idyll is a lie. This is the last day of June 1916 and tomorrow these clean-limbed boys will climb from their trenches to the bloody battle of the Somme. Sir Herbert James Gunn's The Eve of the Battle of Somme, painted in the field, is both a haunting social document and, in its profound contrast with the polished society portraits for which the artist is better known, a pointer to the dual personality of this long-neglected painter.

James Gunn is two distinct artists. He is Sir James Gunn, the self-assured painter of those visual hagiographies which defined Academic style between 1930 and 1950. Yet he is also "Heb" Gunn, the talented impressionist painter with an eye for anecdote; as passionate as his alter-ego is anodyne.

It was as an impressionist that Gunn studied in France in 1912 and travelled in 1914 to Spain and Algiers. In the most astonishing painting of this period, From My Window, Ronda, he captures perfectly the intense white light and heat of the hottest of Spanish afternoons, taking for his subject only a bench and two trees. None of his later works ever come close to the simple perfection of this early work.

It was a combination of the effects of war, love and critical opinion that turned him, of all people, into the man in the stiff collar, striped trousers and spotless white overall who stares from a 1930s photograph, looking more like a senior registrar than a painter. Gunn returned to painting only tentatively after the Great War, in which he was badly gassed: his landscapes of the 1920s are pedestrian and lacklustre. In 1925, his separation from his first wife, Gwen, compounded his decline into apathy.

It was only in 1929 that James Gunn Mark II made his debut. The artist needed funds to marry his second wife, Pauline, and his exhibition at the Fine Art Society was a commercial flop - but the critic of the Daily Telegraph had kind words for his portraiture. He abandoned the unfinished landscape on his easel and set himself to becoming a portraitist, aspiring to out-do Orpen, Lavery and the rest in likenesses of a photographic verisimilitude, calculated to appeal to the sort of personality (and there were many) who required immortalisation without criticism.

But there was more to Gunn's reworking of his own persona than mere pragmatism. Gunn always refused to acknowledge, even to his family, his experiences in the war, or of his first marriage. Taking relish in the depiction of the emeralds and ermines displayed by Pauline in the Yellow Dress (1944) - and an endless queue of sitters, including one king, two queens and four prime ministers - he was able to lay to rest his former self. Portraiture was more than an art form or a profession. It was, as he put it, a way of escape, "a steadying force... traditional and sane".

n Fine Art Society, New Bond St., W1 (0171-629 5116) to 21 April