David Charles Purley was born on 26th January 1945. His father, Charles Purley, was the founder of LEC Refrigeration. 

After a brief period working other jobs, David decided to join the army as an Officer Cadet. He completed his first course of parachute jump training between the 15th and the 24th August, 1966, completing two drops from a balloon and five from a Hastings aircraft. Thereafter, David was promoted to 2nd Lieutenant on 16th December 1966 and posted to the 1st Parachute Battalion. He completed a second course of training from 22nd to 26th May 1967. No mention can be found in either of these courses of an incident in which "his parachute became tangled with that of his instructor" and they both had "a heavy landing" (an anecdote recorded in Motorsport Magazine). However, these details are not always recorded. 

In 1967, Purley was deployed to Aden where he fought the increasingly bitter opposition served up by the FLOSY and the NLF. Constant grenade and blindicide attacks there left an indelible mark on Purley, but also endowed him with a coolness in the face of danger that he carried into his motorsport career. By 1969, he was the commander of the Parachute Regiment Depot, where he was in charge of a guard of honour at Pegasus bridge. Purley resigned his commission on 24th December 1969 and left the army. 

Purley raced in various series between 1970 and 1973 before hiring a March Engineering car and racing it under the family name of LEC Refrigeration Racing in Formula One. Whilst the car was not particularly competitive, Purley was destined to be remembered for actions unrelated to racing. At the Dutch Grand Prix in 1973, he was running directly behind the car of compatriot Roger Williamson. When his car overturned and caught fire, Roger was left alive inside the wreck. Purley immediately abandoned his race in an attempt to save the life of a man he referred to the following day as "a very good friend of mine". He sprinted for the burning car, attempting in vain to turn it upright and extinguish the flames. Despite his bravery, the on-track marshals were not equipped with the flame retardant equipment to help him. He described what happened in a 1975 interview:

"His front tyre burst and he left the track and hit the Armco barrier which bent over and turned his car over upside down and the thing caught fire. I think it happened on lap 13. I had hung back to about 30 yards behind Roger because I was aiming to slipstream past him on that straight and I suddenly saw him swerve off the road and hit the barrier and overturn. I was hard on the brakes trying to avoid wreckage and wheels and things that were all spread across the track. I stopped on the opposite side of the road and just started running towards the crash which had started burning. By the time I got there there was only a small fire there, in effect round the back end of the gearbox where the fuel tanks had ruptured. The trouble was that there was a fire engine and an ambulance only about 200 yards up track from where it happened but they couldn't get to where we were because of the Armco barrier; they were on the inside of the circuit. It wouldn't have happened in England I can assure you".