Simon Pegg jilts his pregnant fiancée at the altar, but comes to regret it five years later when he meets the new man in his ex-girlfriend's life, a successful American hedge fund manager. Pegg, worried that the new man will supplant him in his five-year-old son's affections, plans to win his former girlfriend back by running the London Marathon. With a fortnight's training. And entirely predictable results.

Having enjoyed Shaun of the Dead and Hot Fuzz, I was really looking forward to this one. But sadly, it falls well short. It's difficult to muster much sympathy for Pegg's character, and Hank Azaria (voice of Moe the Bartender, Apu and Chief Wiggum in The Simpsons) is wasted as Pegg's rival. Dylan Moran is dull, too. Thandie Newton looks gorgeous, but that's not really enough.

I'm amazed that this has done so well at the British box office. But if I were you, I wouldn't bother.