The actor played Leonardo da Vinci in Da Vinci's Demons, the American historical fantasy drama series which presented a fictional account of Leonardo da Vinci's early life. Other roles include playing Romeo in St Trinian’s 2: The Legend of Fritton’s Gold alongside David Tennant, Raymond Boynton in Agatha Christie's Poirot: Appointment with Death, Dave Beethoven in the BBC's Freezing and Dr Laurence Shepherd in Monroe the ITV British medical drama series.
The new edition of Doctor Who Magazine reveals that joining Riley in the episode will be actor Trevor Cooper, who last appeared in Doctor Who in 1985 when he played Takis in the Sixth Doctor story Revelation of the Daleks. Other guest stars include Ian Halland, who played director Richard Martin in last year's docu-drama An Adventure in Space and Time; David Benson, who played Noël Coward in the 1998 comedy Goodnight Sweetheart; Sabrina Bartlett, who plays Hannah in Channel 5's Suspects; and Roger Ashton-Griffiths, best known for numerous film roles, including Terry Gilliam's The Brothers Grimm and Martin Scorsese's Gangs of New York.
The episode will be written by Mark Gatiss, who recently confirmed he has been commissioned to write two new episodes. It will form part of the third production block of the series, directed by Paul Murphy, whose work includes Wizards vs Aliens, Trollied, Casualty, Waterloo Road and Grange Hill.
The second episode of the third production block is episode 6, which will be written by Gareth Roberts, whose previous stories include The Shakespeare Code, The Unicorn and the Wasp, Planet of the Dead, The Lodger, and Closing Time as well as a number of episodes of The Sarah Jane Adventures.
Guest stars in episode 6 include Nigel Betts, who played Eddie Hope in Emmerdale, Edward Harrison, who has appeared in many stage roles as well as appearing in Doctors; Andy Gillies, who appeared in Love Soup, Ellis George and Jimmy Vee, a veteran of Doctor Who whose previous roles include the Graske, the Moxx of Balhoon and Bannakaffalatta in Voyage of the Damned.
The readthrough for the episodes took place on Thursday 20th March in Cardiff, with recording now taking place.