Details of the six-kilometre queue and mammoth 24-hour-a-day security operation needed to allow hundreds of thousands of mourners to view the Queen's coffin have been revealed.
The lying-in-state of Queen Elizabeth II will start at 5pm on Wednesday (2am Thursday AEST) and stay open 24 hours a day until 6.30am on the day of the monarch's funeral, September 19, although the queue will close much earlier.
In advice released late on Tuesday evening (Wednesday morning AEST), the UK's Department for Digital Culture, Media and Sport said the queue would begin at London's Albert Embankment, across the Thames from where the Queen's coffin will be in Westminster Hall.
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It's then expected to wind its way about 6.7 kilometres along the south bank of the river, past the London Eye, National Theatre, Tate Modern and HMS Belfast and into Southwark Park.
The government didn't say how long it was expected to take mourners to get to the front of the queue but said there would be length and time estimates posted regularly on social media.
There will be toilets set up along the route, a big screen playing archival footage of the Queen at BFI Southbank, and businesses are expected to stay open beyond normal hours to cater to people in the queue.
Even once mourners get to the Albert embankment, the waiting is not over.
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They'll have to pass through the embankment, across the Lambeth Bridge, into Victoria Tower Gardens and then through "airport-style security" before entering the Palace of Westminster.
It's a mammoth task requiring 1000 volunteers, stewards and Metropolitan Police officers to supervise.
"Once inside the Palace of Westminster, people will be able to walk past the coffim, which will be raised on a catafalque and draped in the Royal Standard, with the orb and sceptre placed on top," the department said, in a statement.
"It will be guarded around the clock by a vigil of units from the Sovereign's Bodyguard, the Household Division and Yeoman Warders of the Tower of London."
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Scouts, Samaritans, The British Red Cross, First Aid Nursing Yeomanry, The Salvation Army and "faith representatives" will be stationed along the queue to help.
"We've got 120 young Scouts volunteers from across the UK who are stepping up to support everyone who'll be paying their respects to Her Majesty The Queen in London this week," Scouts chief executive Matt Hyde said.
"Scouts have a long history of supporting the nation and serving our communities. We're honoured to play our part."
The government said the queue would have step-free access and there would be a separate accessible route starting at the Tate Britain.
St John Ambulance will run eight first aid stations along the route.
Samaritans will have "listening volunteers" on hand in the queue and other places of public mourning to help people process their emotions.
"We know that this news will affect people in different ways, it might be that they are reminded of their own experience of loss or the news has triggered other feelings that people would like to talk about," chair of Samaritans Keith Leslie said, noting the King is the patron of the organisation.
"We know the value of listening and the power of human connection, particularly at times like this, so we encourage anyone struggling with the news to open up – whether that's with Samaritans, a friend or a family member.
"It can help work through what you are facing and put things into perspective."
