Mourners wishing to pay their final respects to the Queen have been warned to expect long queues.
Details have been revealed about how people can attend the lying-in-state, which will take place at the Palace of Westminster.
Large crowds are expected and there are warnings those wanting to take apart in the historic occasion may have to wait for hours and even overnight.
People are advised to bring food and drink as well as suitable clothing.
The lying-in-state begins at 17:00BST on Wednesday and will last until 06:30 on Monday, 19 September – the day of the Queen’s funeral.
It will be open 24 hours a day between those times.
The last member of the Royal Family to lie in state in the hall was the Queen Mother in 2002, when more than 200,000 people queued to view her coffin.
The Queen’s funeral will be “living tradition in action”, the Dean of Westminster has said.
The Very Reverend Dr David Hoyle said it would be “an opportunity for us to give thanks for an extraordinary life… and an opportunity, if you like, for us to give the grief somewhere to go.”
Since the Queen died peacefully at her Balmoral home on Thursday thousands of mourners have been leaving floral tributes at places she loved, including at Buckingham Palace, Sandringham House and Windsor Castle.
Crowds gathered to watch the Queen’s funeral cortege travel from Balmoral to Edinburgh on Sunday, as her coffin began its journey to London ahead of the funeral.
On Monday members of the Royal Family will follow behind the hearse as it travels to St Giles’ Cathedral in the Scottish city, where the Queen’s coffin will lie under vigil for 24 hours.
There will be a service and the coffin will rest at the cathedral for 24 hours for members of the public to pay their respects, before it is flown back to RAF Northolt to then make its way on to Buckingham Palace.
During the lying-in-state period the Queen’s closed coffin will rest on a raised platform inside Westminster Hall in the Houses of Parliament.
People are being warned that they will need to stand for many hours, possibly overnight, with little opportunity to sit down as the queue will be continuously moving.
There are also expected to be delays on public transport and road closures around the area.
Visitors, who will be required to go through airport-style security, are only allowed to bring one small bag with a single opening or zip per person and there are restrictions on what can be taken in.
People are asked to respect the dignity of the event including by remaining silent while inside the Palace of Westminster and dressing appropriately – with clothes “with political or offensive slogans” banned.
People will be asked to turn off their mobile phones or put them on silent mode and to keep noise to a minimum.
Filming, photography and the use of mobile phones or other devices will not be allowed in the security search area or the Palace of Westminster.
Those queuing are also asked not to attempt to queue on behalf of others or leave personal items unattended in the queue.