Question: Which English actor and producer guest-star in the third episode of the eighth series of "Doctor Who"?
Context: "Dark Water" is the eleventh episode of the eighth series of the British science fiction television programme "Doctor Who".  The episode was written by showrunner and head writer Steven Moffat and is the first of a two-part story; the concluding episode is "Death in Heaven", the finale of the eighth series.  It was first broadcast on BBC One on 1 November 2014. "The Waters of Mars" is the third episode of the 2008–2010 specials of British science fiction television series "Doctor Who", broadcast on BBC One on 15 November 2009.  It aired on BBC America on 19 December 2009 and was released on DVD and Blu-ray in the UK on 11 January 2010 and in the US on 2 February 2010.  The story is set on Mars in the year 2059 where the Doctor encounters the first human colony, Bowie Base One.  This is commanded by Captain Adelaide Brooke who turns out to be a pivotal character in the history of humanity.  The Doctor must decide whether to use his knowledge of her fate to change history.  According to "Doctor Who" writer and producer Russell T Davies, the special is closely linked to the next two episodes but is not the first part of a three-part story.  The special was dedicated to Barry Letts, the former writer and producer of "Doctor Who" who died in October 2009.  The episode won the 2010 Hugo Award for Best Dramatic Presentation, Short Form. The eighth series of the BBC family sitcom "My Family" originally aired between 11 April 2008 and 24 December 2008.  The series was commissioned following consistent ratings from the seventh series.  The opening episode, "The Parent Trap", re-introduces the seven main characters.  All episodes from the eighth series are thirty minutes long, excluding the Christmas special.  Two episodes from the series ("One Step Too Far" and "King For A Day") remain unaired, as due to their poor outcome, cast members Robert Lindsay and Zoë Wanamaker requested they were not broadcast.  It is unknown whether these episodes still exist or if they were destroyed by the production company.  The series was once again produced by Rude Boy Productions, a company that produces comedies created by Fred Barron.  The series was filmed at Pinewood Studios in London, in front of a live audience. Madge Delilah Harvey (also Barron) is a fictional character from the British ITV sitcom, "Benidorm", written by Derren Litten.  Madge is portrayed by Scottish actress Sheila Reid, and was one of the primary characters in the show, appearing in every episode of the series since its inception in 2007 until her departure in the second episode of series 7.  Madge returned for a special guest appearance in the third episode of the eighth series.  She will return permanently in the tenth series.  Madge is portrayed as a mean-spirited and acid-tongued pensioner, and is known for her chain-smoking and her trademark usage of a mobility scooter, despite being able-bodied. "Robot of Sherwood" is the third episode of the eighth series of the British science fiction television programme "Doctor Who", written by Mark Gatiss and directed by Paul Murphy, and first broadcast on 6 September 2014.  The episode stars Peter Capaldi and Jenna Coleman, with Tom Riley and Ben Miller guest-starring. Rupert "Danny" Pink is a fictional character created by Steven Moffat and portrayed by Samuel Anderson in the long-running British science fiction television series "Doctor Who".  He is a supporting character in the eighth series of the program, first appearing in the second episode, "Into the Dalek".  He appears alongside Peter Capaldi's Twelfth Doctor and his storylines stem primarily from being the colleague, and later boyfriend, of companion Clara Oswald, portrayed by Jenna Coleman.  He appears in every episode of Series 8 except for the series premiere "Deep Breath" and the third episode "Robot of Sherwood". Joanna Portman (1979–2010) was a fictional Field Operative in the Counter-Terrorism department at MI5, featured in the British television series, "Spooks", also known as MI5 in the United States.  She was played by Miranda Raison.  A former aspiring journalist, she joined the team in the fifth episode of series 4 after being recruited by Adam Carter; Jo retained her journalist occupation as her MI5 cover.  She was killed in a volatile hostage situation in the third episode of the eighth series. Tom Riley (born 5 April 1981) is an English actor and producer. Nigel Betts is an English actor who has an irregular recurring role in ITV soap opera "Emmerdale" as Sales Manager Eddie Hope.  He plays Tony in the BBC Two sitcom "Boy Meets Girl" and had a recurring role as Mr Armitage in the eighth series of "Doctor Who" as well as in Class the current Doctor Who spin-off. The following is a list of characters who appear in the eighth series of the BBC school drama "Waterloo Road", in order of appearance.  The Eighth Series consists of Thirty Episodes, first broadcast from 23 August 2012 to 4 July 2013.  New Main Cast Members from Episode One include Head of English (later Head Teacher) Christine Mulgrew and History Teacher Audrey McFall, with Maggie Croft (later Budgen) and Lorraine Donnegan also promoted to the Main Cast.  New Pupil Characters from Episode One include Christine's son Connor Mulgrew, Imogen Stewart, Jade Fleming, Lula Tsibi, Rhiannon Salt and Angus Hancock.  Head of rival school Havelock High Gerald Findlay also appears in the first five episodes.  Episode four sees the first of several appearances of Imogen's mother Sally Stewart; Michael Byrne's father Billy debuts in the same episode, and appears until his death in Episode Ten.  Pupil Liberty Gordon first appears in Episode Five, and Kevin Skelton (later Chalk) also joins the supporting cast in Episode Eight.  Lorraine's sister Sonya Donnegan joins the main cast as School Secretary from Episode Nine.  Episode Eleven sees the Barry family, consisting of mother Carol and her children Barry, Dynasty and Kacey all join the supporting cast, with pupil Jack MacAllister also debuting in the same episode.  Towards the end of the series, supporting characters of Maintenance Assistant Ndale Kayuni, Dynasty's former boyfriend Steve-O Malone and Acting Head of Science Esther Fairclough all appear.  Angus Deayton and Richard Mylan join the cast as Head of Modern Languages George Windsor and Deputy Head Simon Lowsley in episodes Twenty-Seven and Twenty-Nine respectively.  Recurring Character Robert Bain, Head of Greenock Education makes his first appearance in episode Twenty-Seven, and wife of George Windsor, Princess first appears in episode Twenty-Nine.
Answer: Tom Riley