Among the 2,000 in the congregation will be everyday heroes including NHS staff who toiled tirelessly during the pandemic, British armed forces veterans awarded the highest honours for bravery, and charity workers who have transformed the lives of those less fortunate.
The doors to Westminster Abbey will open at 8am, three hours before the service. Her Majesty’s coffin will leave Westminster Hall at 10.35am.
Late-Night rehearsal held for Funeral of HM Queen Elizabeth II
The state gun carriage will bear her casket, drawn by 98 Royal Navy sailors in a tradition dating back to the funeral of Queen Victoria.
After the funeral, she will be borne by a tremendous procession, featuring more than 4,000 military personnel, that will slowly wend through central London.
The spectacle is expected to become the most watched event in television history with billions tuning in across the world.
Policing the funeral will be a bigger operation the London Olympics in 2012, according to a Scotland Yard chief.
The “hugely complex” operation is the biggest ever mounted by the Metropolitan Police, said Deputy Assistant Commissioner Stuart Cundy.
As well as the 10,000 uniformed officers on duty, snipers will be stationed on rooftops and drones will provide security chiefs with constant visual updates.
Working with a range of other agencies, the Yard has drawn up contingency plans to deal with a range of challenges including terror attacks, criminal activity, crowd surges and crushing.
Mr Cundy said: "This will be the largest single policing event that the Met Police has ever undertaken.
"As a single event this is larger than the 2012 Olympics, it is larger than the Platinum Jubilee weekend.
"The range of officers, police staff and all those supporting the operation is truly immense."
The six surviving former British PMs who served under the Queen will attend, along with Ms Truss.
European leaders will include French president Emmanuel Macron, German president Frank-Walter Steinmeier, Italian president Sergio Mattarell and Finland’s Sauli Niinistö, as well as European Commission president Ursula von der Leyen and European Council president Charles Michel.
Ukraine president Volodymyr Zelensky’s wife Olena is also set to be there - while neither Russia nor Belarus have been invited.
The military regime of Myanmar, accused over deaths of democracy campaigners, have also been left out, while Iran will have only an ambassador.
Westminster Abbey could not fit all the heads of state the Queen met in her lifetime, so former US presidents Barack Obama and Donald Trump were also not invited.
In London, a giant screen has been erected in Hyde Park to show the funeral.
Other cities showing the funeral on outdoor screens include Manchester (Cathedral Gardens and Exchange Square), Birmingham (Centenary Square) and Edinburgh (Holyrood Park).
The Royal Shakespeare Company, of which the late Queen was patron, will screen the funeral at its theatre in Stratfordupon-Avon. The Curzon and Arc cinema chains will host free screenings. Most of the nation’s cathedrals will be broadcasting the funeral and holding special services.