Blake was born on 24 February 1978 in London and attended the Dolphin School in Reading, Berkshire until 1993, before going to St Paul's School in West London on an academic scholarship. He then attended Jesus College, Cambridge, where he studied English and Medieval Italian, graduating in 2000. While a student he acted on both stage and screen, playing Paul Etheridge in White Chameleon, Fleance in Macbeth, and Augustus in Tom Stoppard’s Arcadia (1996) at the National Theatre in productions directed by Richard Eyre and Trevor Nunn.
Ritson played the banjolele on Douglas Hodge's 2006 album Cowley Road Songs, which was recorded in four days at the Blue Moon Studios in Banbury. He describes the banjolele as "a Hybrid instrument between a ukulele and a banjo; teamed up with the gazoo it’s a winning combination."
The Ritson Brothers were selected for the front cover of Screen International's Stars Of Tomorrow 2009.
Ritson is best known in recent years for playing King Edward III in the TV miniseries World Without End (2012), the Duke of Kent in Upstairs Downstairs (2010-2012), Mr Elton in the 2009 BBC adaptation of Emma, Edmund Bertram in the 2007 ITV adaptation of Mansfield Park, Giles Vicary in the BBC series Red Cap and for portraying sidekick Robert Presley in A Touch of Frost. He also played the part of Justin in The League of Gentlemen, Idek in God on Trial, and the comic lead in For Elsie, an Oscar-winning short film, which he also co-produced. He also portrayed the main antagonist in David Goyer’s Da Vinci’s Demons (2013).
In 2013, Ritson appeared as Colonel Brandon in Helen Edmundson's BBC Radio 4 adaptation of Sense and Sensibility.
Ritson is engaged to Actress Hattie Morahan, whom he met at Cambridge University. They have a daughter, Amity, born in August 2016 and are living in North London. Ritson is the brother of Dylan Ritson, with whom he directs and writes.
