Hi Paul. I'm exaggerating a wee bit about the incident. It wasn't quite on a par with the U2 business
And of course, Lightning/Bear intercepts were happening regularly but this was a civil passenger aircraft on a scheduled flight. It was a bit scary at the time, though.
I didn't keep a record of the flight but it was mid-70s and we were in a VC10 en-route to London somewhere near Sofia about lunchtime. I was silver-serving some greens to a First Class punter on the starboard side. In a terribly British restrained manner he nodded his head out of the window and said, "I suppose the chaps up front know about this?". I bent down to look out of the window and nearly dropped my brussels sprouts because there was an armed, silver Mig with a red star on the tail flying parallel to us about 200 ft from the wingtip. You need to have lived during the cold war to appreciate the concern as the Russians were our enemies and we had lived for many years with the expectation of a nuclear war breaking out.
The first contact was ATC who said they could do nothing about it, so the flight crew contacted Ops in London who patched them through to the Foreign Office who immediately contacted Moscow. Meanwhile, to our relief, the Mig slipped behind, only to re-appear a couple of minutes later on the Port wingtip. It also slid underneath us at one stage and popped up on the other side. The poor pilots didn't know which way to look next. The most important thing was not to change course!
It stayed with us for around 20 minutes and then disappeared - I assume that the diplomatic hotline call had done the trick. It sounds quite fun now but in the tensions of that time it was easy to imagine it turning ugly.