The most complex security operation London has ever seen is under way. The Queen is lying in state, and thousands of people are on the streets of the capital queuing to pay their respects, with many more to come.
In the hours and days ahead of the funeral on Monday, the Japanese emperor, kings and queens, the U.S. president, and heads of state from across the globe will assemble in London. They will then all go to Westminster Abbey, which does not have any permanent security perimeter, for a very public funeral.
All of this will be played out in front of hundreds of millions of television viewers around the world, providing a tempting target for international terrorists. It has required a security response unprecedented in scale. MI5 and GCHQ are working behind the scenes with counterterrorism police. The Metropolitan Police has reinforcements from forces across the country, and military personnel and civilian stewards are all playing a role.