Suppose the opportunist Gloder had altogether avoided the Final Solution, and contented himself with some anti-Jewish rhetoric. I was thinking very hard in that period about the difference between Americans and English, and about where I came from, particularly my Jewish roots.

Michael Young is a brilliant young history student whose life is changed when he meets Leo Zuckerman, an ageing physicist with a theory that can change worlds. With Michael and Steve's help, they plan to send a dead rat to poison the well so that it will be pumped clean of the sterilising water.Thus resolving one of the burning questions surrounding time travel: if it’s possible, why do we still have Hitler?

As one half of the Fry and Laurie double act with his comedy partner, Hugh Laurie, he has appeared in A Bit of Fry and Laurie and Jeeves and Wooster.So one of the things I wanted to explore was the obvious question: if that particular sperm had not hit that particular egg, would my family be alive? And of course the second story line about a history student who has just submitted his PhD thesis, was quirky enough and contained all the good parts, the parts where Fry questions things like the relationship between science and art, and how society attributes more importance to one rather than the other. What-if" exercises are interesting when you've got someone to give you proper context along the way. I know that a New York Times reviewer, who gave me a savaging for the book, had no idea I was Jewish and thought I was just a clever English white man, playing games with something as wicked as the Holocaust. As to Leo Zuckerman, his guilt felt real, which really added to his motivation for doing what he did.