The televised raid was the first time the British public had ever seen the Special Forces soldiers in action and elevated them to superstar status.
Action men: Mr Horsfall says of the film: 'What angered me most was the portrayal of the other SAS men.
On the evening of May 5th TV news cut into normal programming to broadcast the beginning of the end of the siege as the SAS soldiers all clad in black abseiled down the front of the building.
Millions watched in awe as they tossed stun grenades into the building to begin their assault.
The raid lasted just 17 minutes and all but one of the six gunmen were shot and killed.
The film is based on Firmin's book about the rescue and he was also an advisor on film which is a co-production between GFC Films and the New Zealand Film Commission.
BBC cameraman Sim Harris was captured scurrying to safety, jumping over a balcony, while smoke billowed from the building after a curtain caught fire.
What was unseen by cameras were the other teams – including Horsfall and Firmin - sweeping through the building in a race to free the hostages before they were shot.
Pictured: Stills from the film showing a reenactment of the siege 'Appalling': Former SAS man Robin Horsfall, who took part in the Iranian Embassy siege, said it was totally wrong for the makers of ' 6 Days ' to claim the film was an accurate re-telling of the events in 1980.
Pictured: Image from the controversial movie 'Laughable': The former SAS sniper, who helped storm the embassy and shot dead one of the terrorists during one of the most watched and admired military operations in British history, lambasted every aspect of the film, which stars Jamie Bell as the SAS hero Who dares: Sim Harris, BBC sound recordist is pictured escaping over a balcony at the front of the Iranian embassy in London at the end of a six day siege by Iranian gunmen.
It also gives the wrong impression to a whole new generation of people who watch the film and take it as being what went on.'What angered me most was the portrayal of the other SAS men.