Born in 1890, and working as a chimney sweep, he became involved in grass-roots social activism from the 1920s until his death in the 1970s. He helped organise the unemployed, moved homeless families into squatted buildings after both world wars and was a key figure in confronting fascism in 1930s Brighton. He also campaigned for cheap food, mobilised pensioners, was involved in running social events and social centres and organising practical aid for the poor and disadvantaged of the town. His actions were based in local neighbourhoods and outside political parties. When Harry died in 1971, 500 people packed Church of St Peter, Brighton, London Road, Brighton for his funeral.
The Cowley Club in Brighton was named after him as a sign of its aim of furthering this tradition of grass-roots organising and class solidarity. The Brighton & Hove Bus and Coach Company has named a bus after Harry Cowley.