Benjafield had a passion for motorsports which started with boating, but moved on to automobiles in the 1920s, following the accidental destruction of his beloved motor launch. Upon purchasing a Bentley 3-litre, he started racing in 1924 and 1925. Benjafield's success led to him being offered to drive a company racer at the behest of Bentley founder W.O. Bentley. He competed in the 24 Hours of Le Mans seven times, and won the event in 1927 with co-driver and fellow "Bentley Boy" S. C. H. "Sammy" Davis; while their car was badly damaged, they frantically made on-the-spot repairs and wound up winning the race.
Benjafield later created the British Racing Drivers' Club, and continued racing until 1936. He died on 20 January 1957.