Around 10,000 police officers could be on duty every day in London, as Queen Elizabeth II's funeral approaches.
It comes as part of the biggest security operation in the United Kingdom's history.
Former Met Police commander Bob Broadhurst, who was the mastermind behind the London 2012 Olympics policing plans said that all leave and training is likely to be cancelled - with extra assistance called in from surrounding forces across the UK.
The Met will also require more specialist officers from abroad, inclusive of close protection and firearms teams - who will all take part in the carefully planned and complex operation.
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The PA News Agency reports that during the Olympic and Paralympic games of 2012, some 10,000 officers were on duty in London each day - with Mr Broadhurst who has over 36 years experience with the Met anticipating similar numbers leading up to the Queen's funeral.
The largest annual policing event for the force is typically the Notting Hill Carnival, in which, around 6,000 officers are on duty. Bob told PA that demand will gradually increase as the week passes, with larger crowds beginning to gather in the capital.
He said: “Clearly you need to manage crowds. Unfortunately large numbers of people also bring in criminal opportunities, so you have to manage crime. You have to manage the basics like lost children, all the other stuff that goes with that.
“Clearly terrorism will be a factor, security is a big issue right from the outset. Not necessarily the more organised terrorist groups but lone individuals, that has to be factored in as well.”
It is expected that mourners will queue for several hours overnight to pay their respects to Queen Elizabeth II, as she lies in state from potentially Wednesday. Some members of the public waited around 10 hours to see Diana, and the Queen Mother in the same position following their deaths.
The Met will also be responsible for the protection of public figures and foreign dignitaries who attend the funeral, and dealing with any protests that their visits may trigger.
Bob added: “By the end of the week you start to click in to what will be, I would say almost certainly, the biggest security operation the country has ever seen. Practically every nation on earth is going to want to send their king, queen, prime minister or president for the funeral.”
Former counter-terrorism national co-ordinator Nick Aldworth told PA that tens of thousands of people arriving around the clock over several days to line routes ahead of any ceremonial event would create the most demand in policing and security terms.
Installing road barriers will be one of the first tasks in anticipation of crowds lining the streets to see the Queen’s funeral cortege pass by. There will be a “significant armed operation”, with officers on patrol and queues formed in a way so people are not crushed and lorries and cars cannot be driven into them.
Rooftop snipers will be in place while the cortege is moving, receiving a helicopter escort anywhere outside of London. Police and security services will be alert to the prospect of knife attacks, bombs being detonated, and all other possible terror threats or incidents.
Mr Aldworth said: “Clearly thousands of people gathered creates an attractive opportunity for any of those methodologies,” but some threats are “easier to manage than others”.
Security screening such as bag checks to look for knives and other weapons will be carried out in some areas.
“We always think about vehicles and blunt or bladed weapons as being the most likely because they’re easy to get hold of and don’t require any skill or planning to use,” Mr Aldworth said, adding that bombs “are less likely” as they are made to order.
Preparations will also involve City of London and British Transport Police, as well as staff from the Royal Parks, Transport for London and Westminster Council.
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