'I began to see myself as alienated from my body. Photographing gave me a kind of power - the power of the observer in her own history.' Faced with terminal illness, Jo Spence derived strength from her use of the camera.

Acknowledged as one of the most radical and influential practioners of modern British photography, she died from breast cancer in 1992 at the age of 58. 'Jo Spence: Matters of Concern', showing at the Royal Festival Hall, highlights the concerns which dominated the last 10 years of her life: health, relationships and class. Some 22 images chart her collaborative work with doctors, therapists, alternative health practitioners, photographers and her husband David Roberts.

Born in London in 1934, Spence never forgot her working-class roots. By the early Seventies, she was a fully-fledged working-class feminist photographer who had progressed from being a secretary for a photographic agency to running her own Hampstead portrait studio. It was with the onset of cancer in 1982 that Spence developed her bravest, most confrontational, work - combining self-medication and complementary treatments with 'phototherapy'. In one of her most striking images, Helmet, she appeared naked (revealing the surgery on her left breast) apart from a motorcycle helmet - a painfully striking revelation of her fear and vulnerability.

She also turned her camera on the lives of her parents and said of the self-portrait (right): 'Being my mother in a boiler suit and turban I began to feel that, for her, work was a release from home into the comradeship of women. I set up some shots of myself, as her, rolling up a cigarette and having her first fag of the day and, as soon as I did that, I realised that was one of the reasons she had bronchitis so often. I had never made that connection.'

This is experimental photography at its best; Jo Spence developed ground-breaking ways of making and using the medium as a powerful means of self-expression. It's uneasy viewing but unmissable.

Royal Festival Hall Galleries, Royal Festival, SE1 (071-928 8800) to 16 Oct, free

(Photograph omitted)