By NBC News

LONDON — Departing Buckingham Palace for the last time, Queen Elizabeth II was escorted by a grand royal procession carrying her coffin atop a gun carriage and past London’s landmarks to the historic hall where she will lie in state until her funeral next week.

Her son Charles, the new king, walked behind the coffin along with his siblings, while Princes William and Harry walked side by side.

Cloaked by the royal standard and adorned by her crown, the queen's coffin was flanked by uniformed soldiers along a ceremonial route lined by flags and vast crowds in the British capital, with Big Ben tolling and guns firing every minute.

Hundreds of thousands of mourners from across the country will then have their final chance to file past at Westminster Hall and say goodbye to Britain’s longest-reigning monarch.

Here’s what to know for Wednesday:

• The queen's coffin was taken in a gun carriage procession from Buckingham Palace to Westminster Hall on Wednesday afternoon.
• Princes William and Harry joined their father, the queen's other children and more royals in following the queen's procession.
• A short service was led by Justin Welby, the archbishop of Canterbury — the head of the Church of England and the ceremonial leader of the worldwide Anglican Communion — assisted by the Dean of Westminster, David Hoyle.
• The public has started filing past the queen's coffin to pay their final respects, with hundreds of thousands expected to say their farewells in the following days.