Question: How many major British awards for children's books did this writer, who wrote the  the second episode of the tenth series of the British science fiction television series "Doctor Who," win?  
Context: "The Doctor Falls" is the twelfth and final episode of the tenth series of the British science fiction television series "Doctor Who".  It is written by Steven Moffat, directed by Rachel Talalay, and was broadcast on 1 July 2017 on BBC One.  It is the second episode of a two-part story, the first part being "World Enough and Time".  The episode received overwhelmingly positive reviews from television critics. "Extremis" is the sixth episode of the tenth series of the British science fiction television series "Doctor Who".  It is written by Steven Moffat and was broadcast on 20 May 2017 on BBC One.  "Extremis" received extremely positive reviews from television critics, with many praising Peter Capaldi's performance and Steven Moffat's script, though some commented on the complicatedness of the script. Cottrell-Boyce has won two major British awards for children's books, the 2004 Carnegie Medal for "Millions", which originated as a film script, and the 2012 Guardian Prize for "The Unforgotten Coat", which was commissioned by a charity. "The Eaters of Light" is the tenth episode of the tenth series of the British science fiction television series "Doctor Who".  It is written by Rona Munro and was broadcast on 17 June 2017 on BBC One.  Munro previously wrote "Survival", the final serial of the original run of "Doctor Who", making her the only writer to date to have worked on the classic and revived eras of the show.  The episode received mixed reviews from television critics. "Thin Ice" is the third episode of the tenth series of the British science fiction television series "Doctor Who".  It is written by Sarah Dollard and was broadcast on 29 April 2017 on BBC One.  "Thin Ice" received mostly positive reviews from critics, with many labelling the topic of racism in the episode as well-executed. "Smile" is the second episode of the tenth series of the British science fiction television series "Doctor Who".  It is written by Frank Cottrell-Boyce and was broadcast on 22 April 2017 on BBC One.  "Smile" received generally positive reviews from critics, with critics commenting on the Doctor and Bill's growing relationship. The tenth series of the British science fiction television programme "Doctor Who" premiered on 15 April 2017 and concluded on 1 July 2017, and consisted of twelve episodes, after it was announced in July 2015 that BBC Worldwide had invested in a tenth series of the programme in its annual review.  The series is led by head writer and executive producer Steven Moffat, alongside executive producer Brian Minchin.  It is the third and final series overseen by the two as executive producers, as well as Moffat's sixth and final series as head writer.  This series is the tenth to air following the programme's revival in 2005, and is the thirty-sixth season overall. "World Enough and Time" is the eleventh episode of the tenth series of the British science fiction television series "Doctor Who".  It is written by Steven Moffat, directed by Rachel Talalay, and was broadcast on 24 June 2017 on BBC One.  The episode received overwhelmingly positive reviews from television critics. Bill Potts is a fictional character created by Steven Moffat and portrayed by Pearl Mackie in the long-running British science fiction television series "Doctor Who".  In the show's tenth series, starting with the first episode, Bill served as a companion of the twelfth incarnation of the alien time traveller known as the Doctor (portrayed by Peter Capaldi). "The Parting of the Ways" is the thirteenth episode of the revived first series of the British science fiction television programme "Doctor Who", which was first broadcast on 18 June 2005.  It was the second episode of the two-part story that featured Christopher Eccleston making his last appearance as the Ninth Doctor and marks the first appearance of David Tennant as the Tenth Doctor.  This is also the last episode to feature Jack Harkness as a regular companion on "Doctor Who".  Jack would appear as a guest companion in the Series 3 finale "Utopia", "The Sound of Drums" and "Last of the Time Lords" and again in the Series 4 finale "The Stolen Earth" / "Journey's End".  The first part, "Bad Wolf", was broadcast on 11 June.
Answer: two