Huge crowds, royalty and a long list of world leaders as well as other dignitaries will all need to be kept safe as part of the mammoth job facing thousands of police officers.
Richard Aitch, director of operations for firm Mobius International, said the risk of a threat is “fairly high” when the King comes into contact with crowds.
It becomes “very difficult” for personal protection officers when the monarch is so close to crowds and they will be carrying out a split second process of “personal vetting” to root out suspicious activity, he said.
"It's the presence of the abnormal"
“As they’re walking along the route, they’ll be looking at hands and eyes," Mr Aitch said of the bodyguards. "They’ll be looking at the demeanour of the crowd. And what they do in their mind is they’ll conduct the process of personal vetting. They will be doing their own vetting of people amongst that crowd.
“They’ll be identifying mannerisms, looking for what looks out of place. It’s the presence of the abnormal, it’s the absence of the normal. Amongst that crowd what you’d want to see is a load of smiling faces, people being open and pleasant to one another and eager to see the King.
“Of course, you could have that one person in the crowd who is maybe sweating profusely, may be looking a bit awkward and fidgeting and that’s the sort of person where you would get on the radio and say you’ve got a suspicious individual in the crowd and give a description. And then a covert operator or a uniformed officer will go in and have a chat with them.”
Mr Aitch said such scenarios, particularly when the person in question is greeting people, are “very difficult” because it “only takes a split second for someone in the crowd to come out with a knife or someone to come out and lunge for whatever reason. And you are on the backfoot immediately.”
He said that part of being a police officer is "understanding people, understanding mannerisms".
The funeral comes at a time when the country’s terrorism threat level stands at “substantial”, meaning an attack is “likely”.
So-called lone actor terrorism, in particular knife attacks, are now considered the main threat but police and security services will be alert to the prospect of knife attacks, bombs being detonated, and all other possible terror threats or incidents.
Members of the public have been urged to report any suspicious behaviour, with security experts describing potential terrorists among the crowds as people who would seem “blatantly out of place” and uninterested in ceremonial events.
Discussing the role of foreign security personnel visiting with dignitaries, Mr Aitch told ITV News that bi-lateral agreements are often in place to allow certain foreign protection units to carry firearms. This is then reciprocated when UK royalty or government officials visit their country.
"Security plans are often questioned, scrutinised and agreed upon during such visits to the UK by foreign heads of state," Mr Aitch explained. "However, today especially when so many dignitaries are co-located, security personnel are too.
"There will be times when too much presence of that security will be detrimental to the atmosphere and venue and so foreign protection units will agree to reduce or handover the security function at that time whilst they remain local, but out of sight."
He said that while covert operatives and special forces operations will only be conducted by UK personnel on British soil, they may still act on worthy foreign intelligence.
Former counter-terrorism police chief Nick Aldworth said it is “probably the biggest operation that we’re likely to mount in the UK”.
The scale surpasses the operation for the Platinum Jubilee weekend and the London 2012 Olympics, which saw up to 10,000 police officers on duty per day.
It is also the largest global protection operation dealt with by the force, with world leaders, dignitaries and other VIPs attending the state funeral.
As of Friday, more than 30 arrests had been made as part of the operation for a range of offences, Mr Cundy said.
Officers from almost every force in the country are helping police in London, with Met Commissioner Sir Mark Rowley – who only took over the role a week ago – likening the possible total number being deployed to the size of West Midlands or Greater Manchester police.
Armed police, motorbike escort riders, officers carrying out patrols on horseback, dog teams and the marine unit are among the specialist teams involved.
Rooftop snipers would be in place while the cortege is moving, accompanied by a helicopter escort anywhere outside of the capital, Mr Aldworth said.
There are more than 22 miles of barriers in central London alone to control crowds and keep key areas secure.
There is also a considerable police presence in Windsor ahead of the Queen’s committal later in the day. Thames Valley Police Assistant Chief Constable Tim De Meyer said more than 2,000 officers will be deployed there in the force’s “largest and most significant” operation.
In the Berkshire town, drones have been used to monitor crowds, vehicle barriers are in place and there will be “airport-style” security checks like screening arches and bag searches.
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