Tanks at dawn on Parliament Square

Tanks were parked in front of the Houses of Parliament early today while soldiers with machineguns blocked a marauding mob dressed like Guy Fawkes.

The scene may have caused alarm to passers-by but it was only Hollywood's version of a futuristic British revolution. Overnight, filmmakers transformed Westminster into the largest location shoot in London for years. Whitehall was closed to traffic as 1,000 people worked until dawn to shoot scenes for a film that promises to be a winter blockbuster.

V For Vendetta, starring Natalie Portman and Hugo Weaving (Agent Smith in the Matrix films), is set in a dystopian Britain with the country in the grip of a totalitarian regime.

The Evening Standard was given exclusive access to filming as director James McTeigue marshalled his tanks, troops and revolutionaries. In the film a masked vigilante (Weaving), known as V, ignites a revolution. Portman, her hair cropped, is the young woman who becomes his ally.

Film-makers had to get permission from 14 separate government departments and agencies, including Black Rod.

Generators rattled and lights were lifted on cranes above Portcullis House and the Treasury. A tank was parked outside the Palace as troops and revolutionaries smoked and waited for the cameras to roll.

Production designer Owen Paterson said: "We have four hours in which we can film. It is quite a rush to get the shots we require."

Eventually, at about 4am, the shoot was dismantled, fake barricades wheeled away, and masked vigilantes sent home. The first commuters appeared, and Westminster was once again the seat of democracy.