About 14 years ago I was flying from Sywell to Thruxton. I was at 2200', about 10 miles to go, in a PA28. I'd been on frequency with Brize, they transferred me to Farnborough a short while ago but Farnborough are too busy to provide any service, that's OK, viz. is great and anyway I'll be talking to Thruxton in a few minutes.
I'm the only one in the aircraft. Cloudbase is over 3000 feet, 3/8 cumulus cloud. Nice day for VFR flying.
I saw an aircraft at about my altitude, quite a distance way, off my port quarter, about halfway between my port wing & astern. Looked at it for a few seconds, it's moving left relative to me so it's going to go behind me. No problem.
A short time later (yes... I should have looked more frequently...) it's still there, and it's a bit larger, and now it's apparent position isn't changing. He has me on his right, he's faster, he should give way but hasn't seen me - and suddenly, he's getting larger very quickly.
I shoved the throttle to idle, pushed the nose down hard, left aileron & right rudder, down I go - and I actually heard his engine as he flew over the top of me a few seconds later. He didn't change course or altitude.
I should have reported it.
The rest of the flight was fine but at Thruxton I had to use both hands to hold the mug of tea....
Edited to add:
At White Waltham, the circuit was/is very busy at times and yet I never had an airmiss or anything remotely close. My instructor drilled it into me that my eyes had to be outside the aircraft pretty much all of the time, and I had to pay close attention to radio calls from other aircraft and to maintain a mental image of who was where. So there were a couple of occasions when following her training meant things went smoothly - on one occasion, I made a slightly early "downwind" call because I could see an aircraft that would have otherwise joined the downwind leg a bit too close for comfort, they instead went behind me (as they should have done). On another occasion I heard someone call "straight in, long finals" instead of joining the circuit (silly bugger) and it was obvious he wasn't going to do anything other than do what he'd said... so I let him do his thing & landed after him.