Queen Elizabeth II left Buckingham Palace on Wednesday for the final time as her coffin began its journey to Westminster Hall, where the late monarch will lie in state.

The queen's coffin, draped in the royal standard and topped with the Imperial State Crown, was borne on a horse-drawn gun carriage out of the front gates of her London residence at 2:22 pm (1322 GMT).

Big Ben tolled and guns were fired at one-minute intervals from Hyde Park as a military band played funeral marches from Beethoven, Mendelssohn and Chopin to accompany the procession to Westminster.

The queen's eldest son and successor King Charles III, his heir Prince William and youngest son Prince Harry followed the coffin on foot as it made the one-mile (1.6-kilometre) journey.

Crowds lined the route, watching in silence, as the cortege passed.

The funeral service of Queen Elizabeth II at London's Westminster Abbey on September 19 will be the culmination of decades of meticulous planning.

Here's what we know so far about how the day will unfold.

- Return to the abbey -

The last time Westminster Abbey was used for a monarch's funeral was for George II in 1760.

Since then, the preferred church has been St George's Chapel at Windsor Castle, but Elizabeth opted for a larger venue.

On the morning of the funeral, the lying in state -- begun at Westminster Hall in parliament on Wednesday -- will continue until 6:30 am (0530 GMT).

The funeral will be conducted by the Dean of Westminster, David Hoyle, with Archbishop of Canterbury Justin Welby giving the sermon.

- Gun carriage -

At around 10:30 am a bearer party will transfer the coffin from the catafalque, a raised platform in Westminster Hall, to a gun carriage which will be waiting outside the north door of Westminster Hall.

The gun carriage will be pulled not by horses but by junior enlisted sailors -- naval ratings -- using ropes.

Members of the royal family will walk behind the coffin to the Great West Door of Westminster Abbey, where it will be carried up the west steps and through the nave to a platform in the choir.

- Major security operation -

Westminster Abbey can hold up to 2,200 people. Those present will include family members, Britain's Prime Minister Liz Truss, senior politicians, former premiers, more than 100 kings, queens and heads of state and other VIPs.

US President Joe Biden has confirmed he will attend, sparking a major security operation.

Biden will reportedly be allowed to travel to the funeral in his armoured presidential limousine, known as The Beast.

Other leaders, such as French President Emmanuel Macron and Israeli President Isaac Herzog, are also expected to have their own transport.

Others, however, will be transported to the abbey by shared bus.

Invitations are expected to be sent to representatives of all countries with which Britain has diplomatic relations.

"Russia and Belarus have not been invited to Queen Elizabeth's state funeral next Monday which will see more than 100 kings, queens, heads of state and other VIPs attend", a government source said.

The source linked this to Russia's invasion of Ukraine.

Military-run Myanmar and isolated North Korea have also not been invited, the source said on condition of anonymity.

There will be no attendance either by representatives from Syria, Venezuela or Taliban-run Afghanistan.

- Journey to Windsor -

After the funeral, the coffin will be drawn on the gun carriage from the abbey to Wellington Arch at London's Hyde Park Corner from where it will continue to Windsor by hearse.

On arrival in Windsor, the hearse will make its way to St George's Chapel via the Long Walk, a historic avenue, for a televised committal service.

The king and senior members of the royal family are expected to join the procession for the last stage of the journey from the Quadrangle in Windsor Castle.

St George's is where Prince Harry and his wife Meghan married in May 2018. The funeral of the queen's husband of 73 years, Prince Philip, was held there in April 2021.

It is also regularly chosen for royal christenings.

- Final resting place -

A private interment service held later will be attended only by close family members.

The queen's final resting place will be the King George VI memorial chapel, which is an annex to the main chapel.

The queen's mother and father -- king George VI and queen Elizabeth the queen mother -- were buried there as well as the ashes of her younger sister princess Margaret.

The coffin of Prince Philip will be moved from the royal vault to the memorial chapel.