I have to say it was my 1982 Range Rover 3.5 4 door. It was the 17th factory production vehicle, and when I bought it in 2007, from its one owner, I paid £250 for it. Full history, garaged all of its life and pristine.
I sold it in 2010 for £3750, having spent no money on it other than the 3 mots that it passed 1st time.
Thought I'd had a result, but I've missed it every day since (not to mention that it's worth £15k+ in today's buoyant Range Rover Classic market.
Now need the torch to tinker with my latest one at the roadside......