Charles Darwin [is my personal favorite Fellow of the Royal Society]. I suppose as a physical scientist I ought to have chosen Newton. He would have won hands down in an IQ test, but if you ask who was the most attractive personality then Darwin is the one you'd wish to meet. Newton was solitary and reclusive, even vain and vindictive in his later years when he was president of the society.
Martin ReesThe physicist is like someone who's watching people playing chess and, after watching a few games, he may have worked out what the moves in the game are. But understanding the rules is just a trivial preliminary on the long route from being a novice to being a grand master. So even if we understand all the laws of physics, then exploring their consequences in the everyday world where complex structures can exist is a far more daunting task, and that's an inexhaustible one I'm sure.
Martin ReesIf we ever establish contact with intelligent aliens living on a planet around a distant star ... They would be made of similar atoms to us. They could trace their origins back to the big bang 13.7 billion years ago, and they would share with us the universe's future. However, the surest common culture would be mathematics.
Martin Rees