For viewers to really engage with the drama The Day Britain Stopped, it had to be believable.
Here, the writer/director, production designer and actors explain how they made everything appear so real.
Gabriel Range: Writer/director
With limited funds and resources to make a film depicting mile after mile of gridlocked traffic and a mid-air collision over Hounslow, Gabriel Range knew he was facing a challenge.
Peter Gordon: Production designer
For Peter Gordon the priority was making both the aircraft collision over a residential street in Hounslow and the traffic gridlock realistic, and he wasn't prepared to compromise.
He insisted on filming the immediate aftermath of the aircraft crash in a real residential street, spending half his budget in 6 hours to do so.
Actress Joanna Griffiths plays air traffic controller Nicola Evans in the film.
To prepare for the role she had to learn all the technical jargon and understand the pressures of the job.
To add to the realism she wasn't allowed to learn her lines and her interview was conducted as if she was talking to a documentary team for real.
Andy Shields: Actor
Andy Shields plays Traffic Police Inspector Clive Turner - the man in charge of the Surrey section of the M25.
He's played many policemen over the years and says the biggest challenge is avoiding using all the old clichés.
Eric Carte: Actor
Eric Carte drew on the experiences of his politician friends for his role as Junior Transport Minister Tom Walker.
Here he explains how he prepared for the part and braved an interview with the BBC's John Humphreys.
The Day Britain Stopped was broadcast on Tuesday, 13 May, 2003 on BBC Two at 2100 BST.