Ours is the Age of Scepticism. So many great men have proved to have clay feet that we have come to believe that anyone whose achievements have brought him to our attention must inevitably be a scoundrel. With intellectuals we are inclined not to accept their work as first-rate unless they display some knavery in their private affairs to balance the transcendent purity of their public deeds.

Thus Stephen Hawking, the pathos of whose physical predicament made him seem a sort of living saint, provided reassurance as to the rigour of his thought when he left his wife in order to marry his nurse. Recent biographies of Albert Einstein have brought to light details of his dealings with his wives and his children which show him to have been something at once less and more than the cuddly teddybear he had seemed up to now – yet the revelations served only to enhance his professional reputation. We prefer our geniuses to wear a little human dirt.

In the case of Sir Isaac Newton, there is hardly any private life for him to have been a bounder in. The first and most momentous phase of his eighty-four years was spent cloistered inside the walls of Trinity College, Cambridge. For the rest, he was the quintessential unsmiling public