War Reserve Constable who joined the Met Police on 3 September 1939. He was based at the Hyde Park Police Station when he was murdered. He was knifed by Frank Stephen Cobbett, a tramp who was received 15 years for manslaughter.
The Met Police have a full report. In summary Cobbett was seen drawing or writing near the war-time anti-aircraft guns in Hyde Park. Avery spoke to him but Cobbett responded with the knife attack. A passer-by and another War Reserve Constable piled in: Cobbett was arrested and Avery taken to St Mary's Hospital where he died the following morning. The report does not explain what Cobbett had been writing and whether, as presumably Avery had suspected, he was a spy.