Ambrose was born in Chipping Norton, Oxfordshire, where his father owned a farm machinery business, and attended the local grammar school.
[2] Ambrose won a scholarship in 1951 to read Engineering at Jesus College, Oxford, and he was given a red MG TC car by his father as promised.
While paired with Peter Riley they devised descriptive route notes "pacenotes" to improve both speed and safety in rallying.
Despite many podium finishes on European rallies, a long held ambition to win a Liege in an Austin-Healey 3000 proved elusive until 1964, when he co-drove with Rauno Aaltonen to win the last Spa-Sofia-Liege, an event lasting four days and nights with no scheduled sleep time.
Ambrose then became a key part of the organising team for the 1968 London-Sydney Marathon and the 1970 London-Mexico Rally conducting reconnaissance and planning of both routes as well as on event management.