Irish actor Allen Leech studied drama and theater at Trinity College Dublin. He appeared in several British television series before making the transatlantic jump as Agrippa in Rome. Downton Abbey reunited him with Maggie Smith and Hugh Bonneville, whom he appeared with in From Time to Time, the 2009 film written by Downton writer/creator Julian Fellowes. More recently, he starred in Mike Leigh's reboot of his acclaimed 1979 play Ecstasy, and is slated to appear in the upcoming thriller, Grand Piano, alongside Elijah Wood and John Cusack.

Of Branson's status change in Downton Abbey Season 3 as Sybil's husband, Leech describes life imitating art. He says, "I was used to just getting into my green uniform every day, and then I arrived this year, and the costume department said, 'You know we're going to have to get you some suits?' Doing my first dining room scene, even as an actor I still felt like, 'I shouldn't be here.' I didn't know what to do with the cutlery and whatnot – which of course is great for the character because he wouldn't know what to do either. Little things kept happening during filming like I wouldn't put my serviette down – and Jim [Carter, Carson] would have to come over and do it."