According to the British police, the state funeral of Queen Elizabeth II is the largest operation in its history.
Nothing compares to the enormously complex task, said Deputy Assistant Commissioner Stuart Cundy of the London Metropolitan Police on Monday.
The scale surpasses both the Queen's platinum jubilee in June and the 2012 Summer Olympics, which saw 10,000 police officers deployed.
At the same time, the state act with hundreds of monarchs, heads of state and government and other high-ranking personalities was the largest security operation that the Met had to deal with.
According to security experts, the greatest danger is currently lone perpetrators, who mainly carry out knife attacks.
The security forces are also prepared for all other possible attacks.
The population was asked to report suspicious people in the crowd.
The main risk is that the closest circle of the royal family follows the Queen's coffin on foot through London for long distances.
More than 3,000 police officers from other parts of the country were sent to London to reinforce.
Police officers on horseback, on motorcycles and with dogs patrolled the streets of the British capital.
To protect the procession, snipers took up positions on rooftops along the route.
A number of streets and subway stations were closed.
Some areas could only be entered with special passes.
A total of 2,300 police officers were to protect the route of the coffin from the state funeral in Westminster Abbey in London to Windsor Castle, where the private burial was planned in the evening.
More than 2,000 officers were also deployed in Windsor.