Early life and Oxford University
Ambrose was born in Chipping Norton, Oxfordshire, where his father owned a farm machinery business, and attended the local grammar school. This business entitled his father to a supplementary allowance for fuel, which was rationed during the Second World War. Ambrose learnt to drive by accompanying his father on his visits to farms, initially sitting on his father's lap to steer whilst his father operated the pedals, and learning map-reading skills (signposts having been removed from roads for fear of invasion).
His father promised to buy him a car if he obtained a scholarship to Oxford University. 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. However, he was not permitted by university rules to keep a car in Oxford whilst he was in his first academic year. Nevertheless, he made friends with other university motor sports enthusiasts and competed in events and rallies outside the university, sometimes in partnership with his elder brother Norman (who had read Physics at Jesus College from 1943 to 1945). In 1952, the brothers were part of the Oxford team for the Annual Varsity Rally, but lost to a Cambridge University team that included Archie Scott Brown.
In the Trinity term of 1952, Ambrose and another Oxford driver, David Hamilton, approached the Proctors for permission to reactivate the University's Motor Drivers' Club, which had been banned before Ambrose started at Oxford for organising a race on public roads between Oxford and Marble Arch in London. He obtained support from Earl Howe and Sir Miles Thomas, both former members of the club. The Proctors gave their permission for the club to be refounded, and it went on to be a source of strength for British rally driving in the 1960s. Ambrose became Secretary, and later President; Earl Howe and Sir Miles Thomas became honorary Vice Presidents.
Rally driving career and later life
After leaving Oxford, Ambrose joined the Royal Air Force but continued to drive in rallies. In 1956, he won the RAC Rally with Lyndon Sims in an Aston Martin DB2. He joined the BMC rally team in 1960, with further successes following. These included victory on the Tulip (Holland, Belgium and eastern France) in 1961 (class victory) and 1964 (outright victory). He also co-drove with Rauno Aaltonen in an Austin-Healey 3000 to win the Spa-Sofia-Liege event in 1964, an event lasting four days and nights with no scheduled sleep time. Aaltonen later recalled how Ambrose had driven 77 miles (124 km) at night in just 52 minutes, reaching speeds of 150 miles (241 km) per hour over cobblestone roads whilst Aaltonen slept in the car. Ambrose also co-drove with Aaltonen as Aaltonen took the 1965 European Rally Championship title, including victory at the RAC Rally. The 1965 RAC Rally victory was the first time that a Mini had won the event.
Ambrose left the BMC team in 1966 to spend more time with his family and his business. His last rally was the 1966 RAC Rally, with Simo Lampinen, although an accident meant that they had to stop. After giving up racing, Ambrose helped with the organisation for the 1968 London-Sydney Marathon and the 1970 London-Mexico Rally. Businesses that he was involved with included a family-run decorating firm and a pub in Wales. Ambrose died in Newbury, Berkshire on 5 January 2008.