Tens of thousands of people are queuing to pay their respects to Queen Elizabeth II as her coffin makes its journey from Edinburgh in Scotland to London later on Tuesday.

Thousands filed past the coffin at St. Giles Cathedral in Edinburgh as the Queen's four children King Charles III, Princess Anne, Prince Andrew and Prince Edward accompanied it in a procession through the streets of the Scottish capital on Monday, before standing in vigil with bowed heads as it lay in state inside the cathedral.

In London, 56-year-old Sri Lankan origin Vanessa Nathakumaran became the first person in the queue that began forming on Monday, way ahead of the Lying-In-State at Westminster Hall in London set to open to the public from Wednesday evening.

I just really wanted to be part of it, said the Londoner, whose family is a great admirer of Britain's royal family.

On Tuesday evening, the coffin will be flown on a Royal Air Force (RAF) plane to London, accompanied by Princess Anne the Princess Royal. It will be received by King Charles III and Queen Consort Camilla, who would have returned from their customary mourning visit to Northern Ireland, and will then lie-in-state overnight at the Bow Room of Buckingham Palace for the royal household to pay their respects.

A ceremonial procession is scheduled for Wednesday afternoon that will see the coffin travel in a gun carriage from Buckingham Palace to the Palace of Westminster, or the Houses of Parliament building.

The procession will travel via Queen's Gardens, The Mall, Horse Guards and Horse Guards Arch, Whitehall, Parliament Street, Parliament Square and New Palace Yard taking in some of the most iconic sites of the UK capital. Several rehearsals have been taking place in preparation for the grand royal procession in London.

During Lying-in-State, the Queen's closed coffin will rest on a raised platform, called a catafalque, in Westminster Hall and will be draped in the Royal Standard with the Orb and Sceptre placed on top. Each corner of the platform will be guarded around the clock by a vigil of units from the Sovereign's Bodyguard, the Household Division, or Yeoman Warders of the Tower of London.

The public will be able to file past the coffin 24 hours a day from 5pm local time on Wednesday until 6.30 am local time on the day of the funeral on Monday. The UK government's Department for Digital, Culture, Media and Sport (DCMS) said those wishing to attend will be required to queue for many hours, possibly overnight .

Large crowds are expected and people are encouraged to check ahead, plan accordingly and be prepared for long wait times. All those attending the Lying-in-State will go through airport-style security and there are tight restrictions on what you can take in, with only small bags permitted, DCMS said of what has been dubbed Operation Feather.

The estimated 5-km-long queue in central London is expected to extend from Westminster to as far as Tower Bridge, with mourners given wristbands in order to take short comfort breaks. Double the estimated 200,000 mourners who turned out following the death of the Queen Mother Queen Elizabeth II's mother in 2002 are expected to descend upon London for the Queen Lying-in-State.

UK Culture Secretary Michelle Donelan told the House of Commons that the DCMS is expecting unprecedented demand .