Why have an affair if the mistress looks like the wife?

The New York Times is sticking to its story. John McCain is sticking to his. They say he had a romantic relationship with a lobbyist, Vicki Iseman, as he worked on his first presidential campaign eight years ago. He says "it's not true". Mrs McCain says she's "very, very disappointed". But what everyone else wonders is, why would he bother?

Ms Iseman is doubtless a good-looking lobbyist. There's just one thing that's slightly spooky about her: to a casual observer, she is the spitting image of Cindy Lou, his wife of 27 years. What's the point of going out for hamburgers, some wonder, when you can have, well, hamburgers, at home?

But if Senator McCain were guilty of the identikit affair, he would not be the first. Chris Tarrant cheated on his wife Ingrid with two women who looked just like her and Boris Becker confused Angela Ermakova for his wife Barbara Feltus in the darkness of a broom cupboard.

Donald Trump replaced Ivana with Marla Maples, Paul McCartney replaced Linda with Heather, and Rod Stewart's wives only differ in that the legs seem to get longer each time he trades one in. And then there's Nicolas Sarkozy.

The French President is suing a newspaper which claimed he sent a text message to his estranged wife, Cecilia, shortly before marrying Italian model Carla Bruni, asking her to come back. Looking at Carla, it's almost as if she has...