There were huge queues along the banks of the River Thames, where people waited to pay their respects to the Queen.
People were told not to set off to see the lying-in-state on Sunday, as the queue reached full capacity. Just after 22:40, the queue was closed to new entrants. At 06:30 BST on Monday the lying-in-state ended.
Here's what else you need you to know about the queue.
At its longest, the wait time was more than 24 hours.
The queue's maximum length was 10 miles – with 6.9 miles from Westminster to Southwark, and a three-mile zigzag queue in Southwark Park.
For updates, the government published a live queue tracker for people to follow on YouTube.
People were warned they would need to stand for many hours with little opportunity to sit down, as the queue is constantly moving.
On Sunday morning, the government tracker advised people not to set off to join the queue as the entry point might soon close. The queue finally closed late on Sunday evening.
People in the queue received coloured wristbands so they could leave for a drink, or go to the toilet, and then return.
Those in the queue were asked not to attempt to save a place for someone else, or leave personal items unattended, or put up tents.
As people passed through Albert Embankment they were directed across Lambeth Bridge, into Victoria Tower Gardens, towards Parliament.
They went through airport-style security before entering Westminster Hall, inside the Palace of Westminster.
There were more than 500 portable toilets at various points along the route.
Local venues and museums – including the Southbank Centre, the National Theatre, BFI Southbank and Shakespeare's Globe – stayed open for extended hours and in some cases for 24 hours, for people to use their facilities.
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People have queued through the night for the chance to pay their respects to the Queen lying in state
Anyone hoping to pay their respects had until 06:30 BST on Monday when the lying-in-state ended.
But organisers warned the queue would be closed well before this so that people did not join the line and fail to reach Westminster Hall in time.
The announcement was published on government social media accounts at 22:41 on Sunday.
The accessible queue reached full capacity at 16:44 on Saturday and was permanently closed, according to the organisers.
The Department for Digital, Culture, Media and Sport said that all time slots for the accessible queue had been allocated and it was permanently shut.
It also asked people not to attempt to join it.
The accessible queue had already been paused on on Friday evening, due to high demand, but entry resumed for several hours from midday on Saturday.
For anyone already allocated a time slot for the accessible queue, step-free access was available to Westminster Hall and guide dogs and other assistance dogs were allowed. British Sign Language interpreters were available.
Visitor assistants in Parliament guided wheelchair users and any people with mobility issues (and their carers) along a route to access Westminster Hall.
Transport bosses confirmed extra train services would be running.
Transport for London said the Westminster area of London would be "exceptionally busy". People were asked to avoid driving into London if possible. Some roads were closed, especially around Westminster itself, which disrupted bus services.
Travel providers said the best way to get around central London was by using London Underground and rail services, although there was the possibility of temporary Tube station closures at short notice, along with special queuing arrangements.
Network Rail said that some London train stations, including King's Cross and London Victoria, would remain open for 24 hours to provide shelter for mourners waiting to take the train home. It added that many toilets, shops and restaurants within the stations would also stay open during this time.
Visitors were advised to plan ahead, check real-time travel information, and consider walking instead wherever possible.
People were also asked to avoid Green Park Tube station unless they needed step-free access.
There was no ticketing system.
There were a number of rules about what you could take into Westminster Hall, and how visitors should behave – there was further information on the Houses of Parliament website.
People did not need to show formal identification to enter the hall, but airport-style security checks were in place.
People were advised to check the weather conditions in advance, and dress accordingly.
They were also advised to bring:
There was detailed guidance about what cannot be brought into the hall, which included:
Any prohibited items would be confiscated and not returned. Police could also conduct security checks along parts of the queue.
Each person was only allowed to take in one small bag with a single opening or zip.
There was a bag-drop facility with limited capacity.
People were asked to respect the dignity of the event, and to remain silent while inside the Palace of Westminster and dress appropriately, Anyone wearing clothes with "political or offensive slogans" would not be allowed in.
Mobile phones and other electrical devices had to be turned off or put on silent mode.
Once inside Westminster Hall, the queue was divided to pass on either side of the catafalque, which is the raised platform where the closed coffin lies.
Visitors were asked to keep moving forward at all times while in line, until they have exited into Parliament Square.
Not inside. Filming, photography and the use of mobile phones or other devices was not allowed in the security search area or once inside the Palace of Westminster.
There were eight first aid stations run by St John Ambulance along the route. They were at Southwark Park, Potters Fields Park, the Tate Modern, the Southbank Centre, Belvedere Road, Archbishop's Park, Lambeth Palace and Victoria Tower Gardens.
And more than 1,000 volunteers, stewards and police officers were on hand to help anyone who needed it. Volunteers were from the Scouts, Samaritans, the British Red Cross, First Aid Nursing Yeomanry and the Salvation Army.
There were water stations along the route, and venues and museums will provide refreshments.
A one-minute silence was held across the UK at 20:00 BST on Sunday 18 September, the night before the Queen's funeral. A two-minute silence will then be observed at the end of the Queen's funeral, at about 11:55 BST on Monday 19 September.
Large numbers of floral tributes have been placed by the public at royal residences around the UK. The Royal Household has issued guidance on where they can be left:
Many local authorities have set up books of condolence in libraries, town halls and other civic buildings.
You can use this link to find your local authority, then visit its website to find out what might be available near you.
There is an online book of condolence on the Royal Family website which can be accessed by clicking here.
BBC News is also collecting your stories and memories of the Queen for our online tributes page – you can share your special moments with us via this online form.
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