Patrick Troughton was attending a Science-Fiction convention when he died in March, 1987. At his last convention panel, he complained of feeling unwell and went to his room to have a rest. A few hours later, one of the convention organizers went to Troughton's room to see why he was late for a convention panel, found him dead of a heart attack in his sleep.
Thanks Kempie and Heatherglen. I did not know either of those two facts, I have a quiz night coming up soon so I will try to retain that info. (Fat chance)
...and his grandson, Jim, plays cricket for Warwickshire and has played a couple of one-day games for England. His other grandson, Sam, is very good actor.