There was a specific account of Stephen Hawking by one of his contemporaries in which Hawking was in his late undergrad or early postgrad.
As I remember, there was a small class of physics students (each one was very capable in their own right) who had been given (I think) ten difficult questions to have a go at. At the next tutorial, the person who was giving the account was very proud that he managed to solve one of them and make significant progress on another. Another person had managed to solve two questions and the tutor was very impressed by this. Stephen showed up late, as he tended to do, and apologised that he only managed to solve eight of them in time.
I remember reading the above tale a long time ago, and thought it was a nice story, but I recently wanted to check if it was true and haven't been able to find any reference to it.