Game of Thrones - Black Mirror - Ripper Street
In 1986 Flynn appeared in the LWT television film London's Burning as firefighter Kenny "Rambo" Baines. When the film spawned a series of the same name in 1988, he was the only member of the main cast who was unable to reprise his role (aside from Gary McDonald, whose own character, Andreas "Ethnic" Lewis, was killed off in the film) due to previous commitments. Also in 1986, he played a minor role as the soldier "Franny" in "The Monocled Mutineer".In 1988 he played the character Freddie in the ITV drama; The Fear which was about the London underworld. He appeared as D.S Eddie Hargreaves for six episodes of the British Academy of Film and Television Award (BAFTA) winning police drama, Between The Lines between 1992 and 1994.
Flynn portrayed Corporal Paddy Garvey of the King's Fusiliers in the ITV series Soldier Soldier. The series began in 1990. He acted alongside Robson Green in the series. After Flynn and Green performed Unchained Melody on the programme, ITV was inundated by people looking to buy the song, and the pair were persuaded by record producer Simon Cowell to record it and release it as a single, a double A-side with White Cliffs of Dover. The single was released under the name Robson & Jerome and reached number one in the UK chart in 1995. It stayed at No.1 for 7 weeks in the UK Singles Chart, selling more than 1.9 million copies and making it the best-selling single of the year, and winning the duo the Music Week Awards in 1996 for best single and best album. The duo had two number one hits in 1995 and 1996 with "I Believe" and "What Becomes of the Brokenhearted" both re-makes of standards, they also produced two number one albums.
Soldier ended in 1997. Flynn went on to star as Eddie Wallis (alongside singing partner Robson Green) in the comedy-drama Ain't Misbehavin' (1997), and was the star of the short-lived police show Badger in 1999. He played Bobby Charlton in the 1999 film Best. On stage, he played Tommy Cooper in Jus' Like That, a tribute to the comic magician written by John Fisher and directed by Simon Callow.
Having semi-retired from acting and moved to Pembrokeshire, in 2007 Flynn directed and starred in the low budget film Rude Tales. The film was split into a series of short stories centered in the lead character, Jerome Rude, played by Flynn. The film was screened at a small number of independent cinemas in the Pembrokeshire area.
After almost 10 years away from acting, in July 2010 it was confirmed that Flynn would be playing the role of Bronn in the HBO television series Game of Thrones, based on the A Song of Ice and Fire novels of George R. R. Martin.
Flynn provides the voice of Daniel (the hound) in the children's television show Tommy Zoom. He also appeared on the television programme So You Think You're Royal?, where it was established that through his mother he is a direct descendant of Oliver Cromwell, through his son Henry Cromwell, and also a descendant of Edward I, Edward II, and Edward III of England.
Flynn stars alongside Matthew Macfadyen in four series of Ripper Street for the BBC.
In 2016, he appeared in "Shut Up and Dance", an episode of the anthology series Black Mirror.