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emergency services in London
Photo: Adam Vaughan/EPA
The state funeral of Elizabeth II is an enormous challenge for the authorities: the police, secret services and anti-terrorist units are coordinating what is probably the largest security operation the city has ever experienced.
Meanwhile, the country has come to a standstill – schools and universities as well as shops and pubs have remained closed almost everywhere.
A police spokesman said the task was "hugely complex" and unlike anything in the city's history - not even the Queen's platinum jubilee this June or the 2012 Olympics Surveillance drones, motorcycle escorts and horse and dog squadrons planned.
More than 10,000 police officers are to ensure order.
Snipers are positioned on the roofs.
A government official told the BBC the effort was comparable to 100 state visits in a matter of days.
The barriers in the city center to direct the crowds are lined up 36 kilometers long, the police said.
Private individuals are not allowed to fly drones.
A large police operation with 2,000 officers, security checks like at the airport and roadblocks are also planned in Windsor.
The police also check phone booths, drains and garbage cans.
kha/dpa