A new video shot by a passerby and obtained by the Guardian captures the moment Ian Tomlinson hits the pavement after allegedly being assaulted by a police officer on 1 April guardian.co.uk

Footage has emerged showing the moment Ian Tomlinson's head hit the pavement after he was pushed over by a police officer at the G20 protests.

The video also revealed fresh details about events leading up to the alleged assault on Tomlinson. It appears to confirm ­witness testimony that the 47-year-old showed no resistance to advancing lines of police in the moments before he was hit and pushed to the ground.

The footage was shot by an anonymous bystander on Cornhill, near the Bank of England. It was handed over exclusively to the Guardian and the Independent Police Complaints Commission, which is ­conducting the criminal inquiry into ­Tomlinson's death.

The four-minute video was shot with a high-quality camera between 7.10pm and 7.30pm on 1 April. There are several moments in the footage that capture Tomlinson, a newspaper vendor who had been attempting to get home when he was pushed over, wandering around the crowd. At no point does he appear to confront police or protesters in an aggressive way, or ­provoke an altercation.

Last night the IPCC attempted to secure a court order to prevent the broadcast of a truncated ­version of the film that appeared ­momentarily on YouTube. The truncated version was copied by Channel 4 News, which planned to broadcast it, before it was removed from YouTube. But a judge refused to grant the injunction.

The IPCC said: "We can confirm that we attempted to seek an injunction this evening against Channel 4 as it came to light that they were due to broadcast ­further evidence which we believe at this moment would potentially damage our criminal investigation into the death of Ian Tomlinson. This injunction was specific to what was due to be broadcast this evening."

The attempt by the IPCC to prevent the broadcast of the video appeared to contradict the stance taken by its chairman, Nick Hardwick, several hours earlier.

Hardwick told MPs on the Commons home affairs select committee yesterday he did not believe web footage of incidents at the demonstrations would prejudice legal proceedings. "We would rather it was not on the web but I don't think it is a serious risk and we have to deal with the world as it is rather than as we would wish it to be," he said.

ITN, which produces Channel 4 News and More 4 News, said the broadcast was "a responsible piece of journalism that brings important information into the public domain." Channel 4 will ­broadcast the short clip tonight.

The full version of the video handed to the Guardian and the IPCC shows the lead-up to the alleged assault on Tomlinson, including an incident in which a policeman appeared to grab a protester. The protester's head was then hit against the door of a police van. That sparked an angry reaction from the crowd, which began running toward Royal Exchange Passage.

A crucial sequence then captures the seconds leading up to the moment Tomlinson is pushed. Tomlinson is seen in the middle of Royal Exchange Passage, facing the advancing lines of police. His hands are in his pockets and he is standing behind a rack of bicycles. When an officer takes a dog close to him, Tomlinson turns his back.

Footage obtained by the Guardian two weeks ago showed how around this time Tomlinson was hit on the legs with a truncheon and pushed to the ground by a Met territorial support group officer. The officer was questioned under caution for manslaughter last week.