The dad of 17 is determined to become the oldest man to complete the grueling 26.2-mile run.
He was in the Army during the Second World War, rising to regimental sergeant major.
Buster’s wife of 35 years, Irana, died in 1955.
He worked in the markets until he was 97. Buster got bored with retirement and landed a job cleaning plumbers’ vans three times a week.
He said: “I will only give up when they put me in a wooden box.”