Dennis has been ringing the bells at his local church in Sunbury-on-Thames since he was a teenager.
He served in World War II. He had the use of his legs saved by an Italian soldier after becoming ill through malnutrition in a prisoner-of-war camp. The Italian lieutenant injected a serum into his lymphatic gland.
But Mr Brock, believed to be the world's oldest active bell-ringer, has never been able to thank the man. He is now actively looking for the mystery Italian soldier who saved his ability to walk, as well as his bell-ringing career.
He only knows his name - Antonino Alessi - and the fact that he was aged around 25 and serving as a "tenente" - or lieutenant - in the Italian army in the Ferrara area in 1943.
He wrote to the hospital after the war but did not receive a reply.
He became ill from malnutrition while interned in a camp in Italy in 1943. A British doctor recommended that he be transferred to a local cottage hospital, where he received the pioneering treatment from the Italian, who had learned it in Abyssinia.
Dennis was told that he may never walk again but he says of the Italian soldier: "If I saw him again, I would take him by both hands and say, 'Look, I'm still walking!' And someone up there has been guiding him and guiding me too," he added.