A five mile queue is expected to pay respects to Queen Elizabeth as hundreds of thousands flock to Westminster this week.
More than 750,000 people are expected to visit parliament from Wednesday, where Her Majesty will lie in state.
The public will be able to visit the coffin in Westminster Hall, which will be accessible 24 hours a day until the morning of the funeral next Monday.
The number of well-wishers on the street is expected to come close to the one million who came out for the funeral of Diana, Princess of Wales, in 1997.
An estimated 200,000 came to see the Queen Mother lie in state at Westminster Hall in 2002.
Security sources told The Times that the operation behind the event will be unprecedented.
In guidance issued this weekend, the government said: “You will need to stand for many hours, possibly overnight . . . as the queue will keep moving.”
Mourners have also been asked to “dress appropriately for the occasion to pay your respects”. The government have said clothes with “political or offensive slogans” are banned.
“Please respect the dignity of this event and behave appropriately. You should remain silent while inside the Palace of Westminster,” it said.
Parts of the parliamentary estate will be closed down for the duration of the four days and security put on high alert for the historic occasion.
Big Ben will toll at 2.22pm as the Queen’s coffin begins its procession down the Mall which is expected to be packed with up to 1m people.
The coffin will be draped in purple and a service of prayer will be led by the Archbishop of Canterbury at Westminster Hall, with members of the Royal Family in attendance.