A series of coded operations have been triggered by the death of the Queen.
While Operation London Bridge is the process between the death of the Queen and her funeral, a series of other operations all form part of the carefully organised arrangements.
The King gives the final approval of the plans.
Here is a rundown of the operations in place:
Operation London Bridge
The process between the death of the Queen and her funeral has the codename London Bridge.
Not to be confused with the nearby famous Tower Bridge, the current London Bridge is a concrete pedestrian and traffic bridge built in the 1970s which spans the River Thames from London Bridge underground and railway station near the Shard on the south side.
A London Bridge features in the traditional 17th century nursery rhyme London Bridge Is Falling Down.
Operation Lion is the overarching plan for any royal death, of which London Bridge is part.
Lion includes London Bridge, as well as Forth Bridge which dealt with the Duke of Edinburgh’s death, as well as Menai Bridge, the contingency plans in case of the Prince of Wales’s death, and arrangements for other royals.
The Queen’s death in Scotland has activated Operation Unicorn, which covers ceremonial events in Edinburgh and the practical arrangements for the return of the monarch’s coffin by RAF plane to London.
Operation Marquee covers the four days of the Queen’s lying-in-state, focusing on the arrangements inside Westminster Hall, including ceremonial aspects, services and vigils.
Thousands of people will queue in the streets as they wait to see the monarch’s coffin on its catafalque. Operation Feather deals with logistics outside Westminster Hall including arrangements for the public.
Operation Spring Tide
Spring Tide covers Charles’ first trip as King to the other three countries of the UK, Scotland, Wales and Northern Ireland, which will take place ahead of the funeral.
There are separate codenames within Spring Tide for the individual arrangements in each country: Operation Kingfisher in Scotland, Operation Dragon in Wales and Operation Shamrock in Northern Ireland.
A spring tide is when there is a high tide and the sun, moon and earth are in alignment and the gravitational force is strong.
These tides occur twice a month near the new and full moon.
An especially high spring tide is known as a “King tide”.
The contingency plan should the Queen have died overseas, when she would have been flown on a C17 RAF plane for repatriation into RAF Brize Norton or Northolt.
The monarch called time on her trips abroad some years ago, leaving royal tours to other members of her family.
Operation Golden Orb
This sets out the blueprint for Charles’s future coronation – a deeply religious affair in Westminster Abbey in many months’ time – which will see Camilla crowned Queen at his side.
It is expected to be more inclusive of multi-faith Britain than past coronations but will be an Anglican service.