Question: The author of the Vesuvius Club plays what role on the HBO Series "Game of Thrones"?

Context paragraphs:
Game of Thrones: Season 4 (soundtrack): The soundtrack album of the fourth season of HBO series "Game of Thrones", titled Game of Thrones: Season 4 was released digitally on June 10, 2014, and on CD on July 1, 2014.  Season 4 of "Game of Thrones" saw the Icelandic band Sigur Rós perform their rendition of "" in a cameo appearance at King Joffrey's wedding in the second episode, "The Lion and the Rose".

The Vesuvius Club: The Vesuvius Club is a 2004 historical spy story by Mark Gatiss.  It is the first novel in a series featuring the spy, Lucifer Box.

Game of Thrones: Season 5 (soundtrack): The soundtrack album of the fifth season of HBO series "Game of Thrones", titled Game of Thrones: Season 5, was released digitally on June 9, 2015, and on CD on July 17, 2015.  The album was composed by Ramin Djawadi.

Game of Thrones: Season 1 (soundtrack): Game of Thrones: Season 1 is the soundtrack album for the first season of HBO series "Game of Thrones".  Composed by Ramin Djawadi, it was released on June 14, 2011 for digital download and on CD.  Djawadi accepted the task 10 weeks before the show premiered, after Stephen Warbeck left the project.  The soundtrack has received neutral to favorable reviews and peaked at #17 on the U.S. Soundtrack Albums chart.  It was nominated for International Film Music Critics Association for "Best Original Score for a Television Series".

Game of Thrones: Season 3 (soundtrack): The soundtrack album of the third season of HBO series "Game of Thrones", titled Game of Thrones: Season 3, was released digitally on June 4, 2013, and on CD on July 2, 2013.  The album was composed by Ramin Djawadi.

Game of Thrones: Season 6 (soundtrack): The soundtrack album of the sixth season of HBO series "Game of Thrones", titled Game of Thrones: Season 6, was released digitally on June 24, 2016, and later released on CD on July 29, 2016.  The album reached No. 1 on the "Billboard"' s Soundtracks chart, and the track from the season finale "Light of the Seven" reached No. 1 on "Billboard"' s Spotify Viral 50 chart.  The "Light of the Seven" is the first time piano is used in the music for "Game of Thrones".  The album was composed by Ramin Djawadi.  The soundtrack has received favorable reviews and peaked at #1 on the U.S. Soundtrack Albums chart and #27 on the U.S. Billboard 200.  It won a International Film Music Critics Association for "Best Original Score for a Television Series".

Black Butterfly (novel): Black Butterfly is the third and final novel in Mark Gatiss' Lucifer Box trilogy, which deals with the exploits of a bisexual British detective and secret agent.  The previous volumes were "The Vesuvius Club" and "The Devil in Amber".

Margaery Tyrell: Margaery Tyrell is a fictional character in the "A Song of Ice and Fire" series of high fantasy novels by American author George R. R. Martin, and its television adaptation "Game of Thrones".  Though a supporting character in the books, she played a more prominent role in the HBO series, and rose to become a main character eventually, where she is portrayed by Natalie Dormer.  Margaery is first mentioned in "A Game of Thrones" (1996) and first appears in "A Clash of Kings" (1998).

Mark Gatiss: Mark Gatiss ( ; born 17 October 1966) is an English actor, comedian, screenwriter and novelist.  His work includes writing for and acting in the TV series "Doctor Who" and "Sherlock".  Together with Reece Shearsmith, Steve Pemberton and Jeremy Dyson, he is a member of the comedy team "The League of Gentlemen".  He is also known for his role as Tycho Nestoris in the HBO series "Game of Thrones".

Game of Thrones: Season 7 (soundtrack): The soundtrack album of the seventh season of HBO series "Game of Thrones", titled Game of Thrones: Season 7, was released digitally on August 25, 2017 on CD on September 29, 2017.

Supporting paragraphs: The Vesuvius Club Mark Gatiss
Answer: Tycho Nestoris