During a live take when filming the external scenes for the fictional 'London Police Station' a member of the public approached supporting artists who were dressed in police uniforms and tried to report a crime that had just taken place. Undeterred by the film unit and cast members advising that a television series was being filmed with fictional characters, the person attempted to report the crime inside the building, not realising that this was a set which had been mocked up to look like a real police station. The building was actually that of the Civil Aviation Authority (CAA) who investigate air accidents and near misses and not routine crime.
Filming for the scenes at the fictional 'London Police Station' took place at the headquarters for the Civil Aviation Authority (CAA) on Kingsway, London WC2.
The external shots of the front of the police station were actually filmed in the service entrance off Wild Street which is at the rear of Kingsway.
The police station is mentioned as being 'South London Police Station' but the real life building is based in the City of Westminster, which is north of the River Thames.
Elfie, the daughter of Karen and David Mars, is played by Molly Simm. She is the real-life daughter of John Simm, who plays David Mars.
Billie Piper, Carey Mulligan, Vineeta Rishi and John Simm have acted alongside David Tennant on the show Doctor Who (2005).
John Simm's character is called David Mars. Coincidentally, he previously starred in the television show Life on Mars (2006), which S.J. Clarkson, the director, also directed.