The Metropolitan Police has been ordered to review the crowd-control tactic known as the “kettle”, which was used to pen in 5,000 people protesting over the G20 summit in London last week.

The Times has learnt that senior Scotland Yard officers who led Operation Glencoe, the plan to protect the summit and prevent disorder, have been summoned to explain their tactics to members of the force’s watchdog body.

Commander Bob Broadhurst and his team will also be questioned at a closed meeting of the Metropolitan Police Authority (MPA) about the death of Ian Tomlinson, who was hit by a riot police officer minutes before he died from a heart attack. Mr Broadhurst, who gave stark warnings of violence before the protests, will also face questions about whether the language he and fellow commanders used served to stoke up confrontation.

The MPA meeting will take place on April 23, amid mounting public concern and complaints about an aggressive police approach to the demonstrations. The officers will also have to appear at a public session of the police authority the following week.

The Independent Police Complaints Commission (IPCC), which is investigating the circumstances of Mr Tomlinson’s death, said yesterday that it had received 120 complaints about the policing of the G20 protests in the City of London. Many complainants were responding to the footage of the apparent assault on Mr Tomlinson, but a significant number were people who were trapped inside the “kettle” — the police cordon thrown around the Bank of England — for several hours and not allowed to leave.

Kit Malthouse, deputy chairman of the police authority, said: “We have asked the Met for a thorough briefing session. We want to review and understand why they employed those tactics.” Mr Malthouse, who is also Deputy Mayor with responsibility for policing, said that members would require a full explanation of the intelligence material that convinced the police that anarchist groups were planning violence in the City. “We need to understand the intelligence picture and decide whether the police response on the day was proportionate,” he said.

The IPCC investigation into Mr Tomlinson’s death is likely to take several months and is focused on amassing video evidence and witness statements. The commission has been accused of making a slow start to the inquiry after it initially left the matter in the hands of City of London Police. It took control of the case itself only after video footage emerged that showed Mr Tomlinson being snapped at by a police dog and hit with a baton before being pushed face forwards to the ground by a masked police officer.

That officer, a member of the Met’s Territorial Support Group, has been suspended. Scotland Yard sources insist that the apparent delay in removing him from duty occurred because it had to adhere strictly to employment procedures. The Met says that it is co-operating fully with the IPCC inquiry.

A second post-mortem examination on the body of Mr Tomlinson, 47, a newspaper vendor, has been carried out at the request of his family. The examination was conducted by Dr Nat Cary, a leading forensic pathologist, whose report has been made available to the IPCC and Mr Tomlinson’s family. No details have been made available publicly.

Protest groups have released further video footage of what they describe as violent police tactics during the demonstrations on April 1.

Organisers of the Climate Camp outside the Carbon Exchange in Bishopsgate said that their protest was totally peaceful until the police surrounded it at about 7pm and attempted to clear the street by force. Protesters held their hands in the air and chanted “this is not a riot” as riot police pushed into the crowd with shields and batons.

Sarah Horne, who attended the camp, said: “Everything was fine until, without warning, riot police suddenly started attacking people at the edge of the camp. After this initial charge, they shut us all in and didn’t let anyone leave until 11.30pm.”

The Met is expected to defend its use of the kettle tactic. Senior officers believe that they contained the threat of disorder that otherwise might have spread across the City. The tactic was first used in London during a May Day demonstration in 2001. Three thousand people were held for up to seven hours inside a police cordon at Oxford Circus without food, drink or lavatory facilities. They were released eventually one by one after being searched and having their photographs taken.

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