My one Tony Hoare (RIP) story:
We got him to keynote our conference one year. We snapped him up afterwards along with a couple of other speakers for dinner, as we usually did, hoping to partake of his wisdom in a more private setting, but Joe Armstrong (also RIP) sat down next to him and started conversing excitedly, and none of the rest of us got a word in edgewise for the rest of the evening.
I realise this was probably more of a Joe Armstrong story.