Question: Who did John Heffernan portray in the British crime drama programme starring Idris Elba?

Context paragraphs:
Luther (TV series): Luther is a British crime drama programme starring Idris Elba as the title character, DCI John Luther.  Written by Neil Cross, the first season, comprising six episodes, ran in May and June 2010.  A second season of four episodes aired on BBC One in June and July 2011.  A third series was commissioned in 2012, comprising four episodes aired in July 2013.  A two-episode fourth series was broadcast in December 2015.  A fifth series has been announced with filming due to start in early 2018.

List of Broadchurch episodes: "Broadchurch" is a British television crime drama programme broadcast on ITV.  It was created and written by Chris Chibnall and produced by Kudos Film and Television, Shine America, and Imaginary Friends.  The first series focuses on the death of an 11-year-old boy and the impact of grief, mutual suspicion, and media attention on the town; it premiered on 4 March 2013.  The second series began its ITV broadcast on 5 January 2015.  The third series was confirmed on 23 February 2015, immediately following the second series finale, and premiered on 27 February 2017, and concluded on 17 April 2017.  During the course of the programme, episodes of "Broadchurch " aired over series.

List of Luther episodes: "Luther" is a British psychological crime drama television series that premiered on BBC One in the UK on 4 May 2010.  The series centres on DCI John Luther (played by Idris Elba), a highly talented detective working in London to solve a series of high-profile murders.  Co-stars include Ruth Wilson as Alice Morgan, Warren Brown as DS Justin Ripley, Steven Mackintosh as DCI Ian Reed, and Saskia Reeves as Det Supt Rose Teller.  As the series progresses Nikki Amuka-Bird joins as the recently promoted DCI Erin Gray, and Dermot Crowley is promoted to a starring role as Det Supt Martin Schenk, and Michael Smiley continues portraying Benny Deadhead.

Beasts of No Nation (film): Beasts of No Nation is a 2015 American war drama film written, co-produced and directed by Cary Joji Fukunaga, who acted as his own cinematographer, about a young boy who becomes a child soldier as his country goes through a horrific war.  Shot in Ghana and starring Idris Elba, Abraham Attah, Ama K. Abebrese, Grace Nortey, David Dontoh, and Opeyemi Fagbohungbe, the film is based on the 2005 novel of the same name by Uzodinma Iweala ― the book itself being named after a Fela Kuti album.

Molly's Game: Molly's Game is a 2017 American crime drama film written and directed by Aaron Sorkin in his directorial debut, based upon the memoir "Molly's Game: From Hollywood's Elite to Wall Street's Billionaire Boys Club, My High-Stakes Adventure in the World of Underground Poker" by Molly Bloom.  It stars Jessica Chastain as Bloom, along with Idris Elba, Kevin Costner, Michael Cera, Brian d'Arcy James, Chris O'Dowd, Bill Camp, Graham Greene, Claire Rankin, Joe Keery and Jeremy Strong.  The film follows the 26-year-old Bloom who becomes the target of an FBI investigation following her running of an underground poker empire for Hollywood celebrities, athletes, business tycoons and the Russian mob.

Ultraviolet (TV serial): Ultraviolet is a 1998 United Kingdom television series written and directed by Joe Ahearne and starring Jack Davenport, Susannah Harker, Idris Elba and Philip Quast.  The music was composed and performed by Sue Hewitt.  The programme was produced by World Productions for Channel 4.

Guerrilla (2017 miniseries): Guerrilla is a six-part British drama miniseries set in early 1970s London, against the backdrop of the Immigration Act 1971 and British black power movements such as the British Black Panthers and Race Today Collective.  It was written and directed by John Ridley and stars Idris Elba, Freida Pinto and Babou Ceesay in leading roles.  "Guerilla" debuted on Sky Atlantic on 13 April 2017 and on Showtime on 16 April 2017.

100 Streets: 100 Streets is a British drama film directed by Jim O'Hanlon and starring Idris Elba.  It made its debut in the United Kingdom on 11 November 2016, before being released in American theaters and on video-on-demand on 13 January 2017 by Samuel Goldwyn Films.

John Heffernan (actor): John Heffernan is a British theatre and screen actor.  He has worked with the English Touring Theatre, the Royal Shakespeare Company, and the National Theatre, taking the lead roles in Edward II at the National Theatre, and Oppenheimer with the RSC.  He has appeared on screen in a number of roles, including Henry Lascelles in the BBC adaptation of Susanna Clarke's novel, "Jonathan Strange & Mr Norrell", Jaggers in "Dickensian" and Steven Rose in the fourth series of "Luther".

Mandela: Long Walk to Freedom: Mandela: Long Walk to Freedom is a 2013 British-South African biographical film directed by Justin Chadwick from a script written by William Nicholson and starring Idris Elba and Naomie Harris.  The film is based on the 1995 autobiographical book "Long Walk to Freedom" by anti-apartheid revolutionary and former South African President Nelson Mandela.

Supporting paragraphs: John Heffernan (actor) Luther (TV series)
Answer: Steven Rose