The Queen Mother opened our RSPCA vets when I was a teenager in the 90s. She was tiny.
I collided with Chris Evans (Virgin DJ, not Capt. America) in Chinatown in London, also in the 90s (Don't Forget Your Toothbrush era). We were both going round a corner in opposite directions, and neither of us was looking where we were going as we were each talking to who we were with. Very tall!
Noel Edmunds twice, but that was because I went to a Deal or No Deal taping twice. The first time I was Pilgrim of the Day, picked because my friend worked on the crew (got to see the room the Banker sat in during my tour too). He was lovely and I made him laugh.
Cuba Gooding Jr. walked past me on a side street just off Times Square in 1998.
Sid Owen at The Blue Rooms in Bath. He was arrogant and shoved his way to the front of the bar queue. So my friend shouted 'Riiiiiccckkkkkaaaayyy' at his back. He looked pissed off about that. Self-fulfilling prophecy. He was very 'do you know who I am'. Yes, we do, but you can't have it both ways. Saw him coming out of Loch Fyne restaurant in Bath in the middle of the day on another occasion.
Tom Baker (Dr Who), though I had to be told who he was as he was before my time. Also in Bath.