The queen's funeral is expected to attract hundreds of thousands of people to London's streets, echoing other important events in Britain's history, including her coronation in 1953, the funeral of former Prime Minister Winston Churchill in 1965 and the death of Princess Diana in 1997.

Stuart Cundy, London's Metropolitan Police Deputy Assistant Commissioner, said the force was preparing for events ranging from terrorism threats to protests and crowd crushes.

He said his force would be deploying the largest ever number of officers on the city's streets and the largest protection operation for world leaders and royals in the police's almost 200 year history, with officers from almost every force in the country deployed.

Among the specialist officers on duty will be divers, dog handlers, police on horses, motorcycle outriders, firearms officers and close protection officers, who will guard leaders and members of the royal family from around the world.

U.S. President Joe Biden and French President Emmanuel Macron are among the most high-profile guests from overseas who have confirmed they will be attending.

Cundy said the massive policing operation would surpass other major policing events in London, including the 2012 Olympics and the celebrations in June for the queen's Platinum Jubilee, which celebrated her 70 years on the British throne.

To give an idea of the scale of the operation, Cundy said 22 miles (36 km) of barriers had been deployed in central London to help control the crowds.

"There’s absolutely nothing that compares to our policing operation this week, and particularly on Monday for the state funeral," Cundy told Reuters. "This will be the single largest policing operation that the Met police has ever undertaken and I think is every likely to undertake."

PROTESTS

The police operation will be overseen by Mark Rowley, who is in his first week in the job as the head of London's police after rejoining the force having previously served as the national lead for counter-terrorism.

London police have so far made 34 arrests in the run up to the funeral, but none of them were related to protests. There has been criticism that in Scotland police had been overly heavy-handed in dealing with those voicing objection.

"People have the right to protest," Cundy said. "Our response will be proportionate, it will be balanced, and our officers will only be taking action where it is absolutely necessary."

Tim De Meyer, the assistant chief constable of Thames Valley Police, who will be in charge of the policing operation in Windsor where the queen will be taken from London to be buried, said the public will face airport-style screening.

"Our contingency planning considers a whole range of different scenarios which includes everything from terror attacks to criminal activity to crowd surges and crushing," Cundy said.

Two police officers were stabbed in an incident unrelated to the funeral, or terrorism, in central London on Friday which he said brought "into sharp focus, the need for all officers who are on duty, the members of the public, to keep that vigilance".