The Queen is now officially Lying in State in Westminster Hall, where she will remain until her funeral on Monday.
Throughout the days ahead, a rotation of bodyguards will keep a 24-hour vigil around her coffin.
Public mourners are allowed to silently and respectfully file past the Queen's coffin to pay their respects, and must keep a distance.
There are three ceremonial units tasked with guarding the sovereign as she Lies in State.
The Gentlemen at Arms were the first royal bodyguards to begin the vigil, and can be seen standing closest to the coffin as Her Majesty rests on the raised platform, known as a catafalque.
The Royal Company of Archers and the Yeomen of the Guard will also stand guard.
The Gentlemen at Arms are the most senior of the sovereign's guards.
The Royal Company of Archers are the sovereign's official guards in Scotland.
While the Queen was lying at rest in Scotland she was guarded by the Royal Company of Archers.
How long do the guards stand watch?
The continuous 24-hour vigil will be broken into four six-hour shifts.
These shifts will rotate, with the guards standing vigil switching places every 20 minutes.
On the first day of the vigil, as Westminster Hall opened to the public, six Gentlemen at Arms stood on the raised platform the coffin was placed on, with four at each corner and two facing forward towards the entrance.
Surrounding the six Gentlemen at Arms were four members of the Bodyguard the Yeomen of the Guard.
Every 20 minutes the replacement Gentlemen and Yeomen take their place before their predecessors depart.A similar system was used in Scotland, with six-hour shifts broken into 20-minute vigils by the Company of Archers.Who are the Gentlemen at Arms?
The Gentlemen at Arms are the most senior group of the sovereign's bodyguards, who accompany the monarch to ceremonial occasions.
They are the more senior of the bodyguard groups in England, and are classed as the 'nearest guard' to the King.
They are traditionally present when the sovereign welcomes foreign leaders, or during the State Opening of Parliament.
They also support the sovereign when they attend services of the Orders of Chivalry or Garter.
The order consists of five Officers (the Captain, the Lieutenant, the Standard Bearer, the Clerk of the Cheque and the Harbinger) and 27 Gentlemen at Arms.
The Captain is a political appointment who is always the government chief whip of the House of Lords.
This means the current occupant, Baroness Williams, has only held the post since September 7 when she was appointed by Prime Minister Liz Truss as part of her ministerial reshuffle when she became prime minister.They wear a dragoon officer uniform, similar to those seen during the 1840s, distinguishable by red coats and golden helmets featuring prominent plumage.
Officers wear gold aiguillettes and carry sticks of office, which they receive from the monarch when they are appointed.
All the Gentlemen wear cavalry swords are worn, and long ceremonial battle-axes, which are more than 300 years old.
While attending the Queen during the Lying-in-State some of them have worn black coats as a sign of respect.
The group was established by King Henry VIII in 1509 and celebrated its 500-year anniversary in 2009.
Who are the Yeomen of the Guard?
The Yeoman make up the oldest established military corps still in service in the United Kingdom.
The corps was established by King Henry VII in 1485 after the Battle of Bosworth Field, which concluded the War of the Roses.
They take part in many similar functions as the Gentlemen at Arms - although their order is slightly larger at 73.
Unlike the Gentlemen at Arms, all members of the Yeoman Guard are former warrant or non-commissioned officers of the British forces.
The King's Guard are the contingents of infantry and cavalry soldiers charged with guarding the official royal residences who tourists flock to see at Buckingham Palace.
They perform both ceremonial and sentry duties at royal residences.
The King's Guard is made up of foot guards drawn from five regiments, including the Grenadier Guards, the Coldstream Guards, the Scots Guards, the Irish Guards, and the Welsh Guards
The Coldstream Guards have also played a role in escorting the Queen's coffin around the country.
Together, they form the oldest continuously serving regiment of the British Army.
The protection of the monarchy is just one of the Coldstream Guards' roles, and they are often seen at royal ceremonial events, and around Buckingham Palace.
They are famous for their tall, fluffy black bearskin hats, and their unflinching discipline against Buckingham Palace tourists' pestering attempts.
Unlike the Gentlemen or Yeomen, the Coldstream Guards are fully active British Army soldiers, and were deployed to the Helmand Province during the war in Afghanistan.
The remarkable life of the Queen remembered in our latest episode of What You Need To Know.