Ministers have rehearsed for the Queen's death for the first time with a secret exercise to prepare for 10 days of national mourning, it has emerged.
The run-through, apparently known as Castle Dove, saw Cabinet ministers and Whitehall officials discuss 'D+1', the day after the monarch's death.
The plan, which is reported to be called London Bridge, came in the week that the 92-year-old Queen pulled out of a service at St Paul's Cathedral because she was feeling ill, although it was not in response to any specific fears about her health.
It was the first time politicians had joined civil servants in the same room to discuss the plans, which would involve the Prime Minister speaking to the country, The Sunday Times reported.
A source told the newspaper that the rehearsal was of an 'unprecedented' scale.
They said: 'This is the first time different ministers have come together in one room. Previously it has only been officials.'
The 92-year-old was due to attend Thursday's event at St Paul's Cathedral which was attended by Hollywood star Angelina Jolie. It is understood no doctor was called.
A spokeswoman for the Palace said: 'The Queen is feeling under the weather today and has decided not to attend this morning's service at St Paul's Cathedral marking the 200th anniversary of the Order of Michael and St George.'
In 2016 - the year she turned 90 - the monarch called time on her overseas travels, leaving long-haul destinations to the younger members of her family.
But she still has a busy diary of events, and in 2017 carried out 296 engagements.
Last year the Guardian reported numerous details about the aftermath of the Queen's death, which would see the entire Privy Council assemble to proclaim the new monarch.
A footman at Buckingham Palace will reportedly pin a notice to the gates while a notice is issued to the world's media and news agencies.
TV and radio stations are also said to have prepared for the news with a ready-to-use playlist of sad and inoffensive music.
Prince Charles will make an early visit to Scotland and Wales in the days and weeks after he becomes King, it is claimed.
The Queen’s body will meanwhile ‘lie in state’, remaining in Westminster Hall to allow members of the public to file in and pay their respects.
This article has been adapted from its original source.
© Associated Newspapers Ltd.