Smiley was born in 1963 in Belfast and grew up in Holywood. He moved to London in his 20s with his wife. He began doing stand-up in 1993, after accepting a bet at an open-mic night. He had worked as a cycle courier (like his character in Spaced) and as an acid houseDJ.
In 2003, he guest starred in the Doctor Who audio drama Creatures of Beauty. In 2004 he appeared in season 2, episode 4 of Hustle as Max the forger. He also was a small character in episode 2 "The Model" of 15 Storeys High.
He has appeared in all three series of The Maltby Collection on Radio 4 as Des Wainwright, an eccentric security guard who keeps repeating himself and reminding people he was in the SAS. He is playing the part of Benny "Deadhead" Silver in the BBC drama series Luther.
it’s Michael... It opens with the audience literally a few steps behind Michael Fassbender’s George – as in Smiley, though his surname is Woodhouse – as he paces purposefully through London after dark.