He participated in 14 World Championship Formula One Grands Prix, achieving one podium finish and won the 24 Hours of Le Mans sportscar race twice.

[3] In 1956, driving for the Scottish team Ecurie Ecosse, he won the 1956 24 Hours of Le Mans, sharing an ex-works Jaguar D-type with Ninian Sanderson.

[5][6] In the early 1960s, the United Dominions Trust made plans to break the record for the time taken to fly from Sydney to London in order to gain publicity for its UDT Laystall racing team.

[7] G-ARKD was abandoned and another CAC Mustang, registered VH-UWB, was bought in Australia for Flockhart to make a second attempt at the Sydney-London record.

[7] On 12 April 1962, while on a test flight in preparation for the record attempt, Flockhart crashed VH-UWB in poor weather near Kallista, Victoria, and was killed.