Run Fatboy Run

Dennis Doyle (Simon Pegg), who jilted his pregnant fiancée Libby on their wedding day five years prior, decides to run a marathon to win her back. He trains alongside his two "coaches", Gordon and Mr. Ghoshdastidar, with the help of Libby's cousin and best friend. Dennis faces his former fiancé Whit (Hank Azaria), now in a relationship with Libby, at the Nike River Marathon in London, ultimately completing the race and winning Libby back.