London Man Who Died at G20 Protest Attacked by Police, Video Shows

Britain's police watchdog is to remove the police from the investigation into the death of Ian Tomlinson during last week's G20 protests and carry out its own independent inquiry, the Guardian has learned.

Earlier this week the Independent Police Complaints Commission appointed the City of London force to investigate the incident, despite its officers having been involved in policing the protest, instead of using its own investigators.

Video obtained by the Guardian of the minutes before Tomlinson's death clearly shows City of London officers standing near the officer who attacked the newspaper seller. That officer is believed to be from the Metropolitan force.

A fresh announcement on the investigation is expected shortly. The IPCC will announce that it will use its own investigators to determine whether Tomlinson was assaulted by police and whether that contributed to his death.

The video footage shows Tomlinson walking past police with his hands in his pockets, then being knocked to the ground by a police officer in riot gear as officers from the City of London force look on, minutes before he suffered a fatal heart attack.

In a statement last Friday, the head of the City of London force declared the policing operation a success, further calling into doubt the force's suitability to conduct the investigation.

Mike Bowron, the City of London police commissioner, said: "The success of the operation is shown in the excellent feedback we have received from across the Square Mile."

There had been intense pressure on the IPCC to use its powers to conduct an independent investigation. Brian Paddick, a former deputy assistant commissioner at the Metropolitan police, demanded that police be removed from the case and said any officer who struck the innocent passerby could face a manslaughter charge.

He said the officers from the City of London force would be key witnesses in the investigation.

Paddick told the Guardian: "How can the City of London do the investigation independently? I'm sorry but there are three City of London officers in that video, how can they do the investigation? It certainly needs to be a full-blown criminal investigation ... [into] whether there is a provable link between the death and assault, because an assault is a criminal offence. Police are allowed to use force, provided it is justified."

Paddick refused to comment on whether the police actions in the video were justified, but said the officer seen striking Tomlinson could potentially face a charge of manslaughter, for which the maximum penalty is life imprisonment. "If it is held that there is a link between the violence he [the officer] was inflicting and the heart attack [suffered by Tomlinson], that then is an assault, resulting in death, albeit unintended. If a court held it is an assault, it is an unlawful action resulting in manslaughter," he said.

Reaction to the publication of the video came from the police and from across the political spectrum. The Metropolitan police commissioner, Sir Paul Stephenson, said today the video images "raise obvious concerns" and should be investigated fully.

Stephenson said the Met would co-operate with the investigation. "It is absolutely right and proper that there is a full investigation into this matter, which the Met will fully support," he said.

The home secretary, Jacqui Smith, defended the IPPC's role in the inquiry, saying there would be a criminal case if necessary: "What's extremely important from the events last week, from the sad death of Ian Tomlinson, is that there is an inquiry through the IPCC," she said. "If it identifies the need for a criminal investigation then that also needs to be pursued."

Boris Johnson, the London mayor, is pressing for a "speedy and thorough" inquiry by the police complaints body, his chief spokesman said. He said the mayor had watched the footage today and had been seriously concerned by what he saw.

Many opposition and backbench Labour MPs had called for a fully independent inquiry into the attack.

The Labour MP David Winnick, a member of the home affairs select committee, said City of London should not be running the investigation. "One thing is quite clear," he said, "the inquiry taking place by City of London police is hardly satisfactory, even if that inquiry is being managed or monitored by the Independent Police Complaints Commission."

The shadow home secretary, Chris Grayling, said the video footage was "extremely alarming and leave[s] big questions to be answered by the police. It's right that there should be an independent investigation. The inquiry must be completed quickly so that any further appropriate action can be taken."

The Liberal Democrat justice spokesman, David Howarth, said: "This video clearly shows an unprovoked attack by a police officer on a passerby. It is sickening. There must be a full-scale criminal investigation. The officer concerned and the other officers shown in the video must immediately come forward."