The government has prepared for the queue to see the Queen lying in state at parliament to be up to 10 miles long.
Up to 1m people are expected to turn out to pay their respects to the late monarch at Westminster Hall, with access to the public beginning at 5pm today and lasting until 6.30am on Monday.
The government has set up infrastructure for 10 miles, with the starting point at Albert Embankment and the end point at Southwark Park.
Seven miles of this will span along the Thames and a further three miles have been planned to zig-zag around Southwark Park.
The queue is already spanning back past Westminster Bridge, with four hours to go until Westminster Hall is open to the public.
More than 1,000 volunteers, stewards and Metropolitan Police officers will be deployed to monitor the queue and provide assistance.
People have been warned they will have to wait “many hours” and “possibly overnight” to see the Queen’s coffin, with some estimates at 30 hours.
The Queen’s coffin will be transported from Buckingham Palace to Westminster Hall in parliament from 2.22pm today in a procession that will begin at Buckingham Palace and go up the Mall.
The coffin returned to London last night, after being flown in from Scotland, where Prime Minister Liz Truss and Princess Anne were waiting at RAF Northolt.