Just a month ago the Chinese president Xi Jinping and the Queen retired to take after-dinner coffee in the scarlet damask splendour of Buckingham Palace's State Dining Room.
But The Mail on Sunday has now revealed that the opulent room will be closed until next summer because its ceiling poses a potential danger to the Royal Family and their guests.
While the room is shut for repairs, engineers are also making an emergency inspection of ceiling space it shares with other famous rooms.
These include The Ballroom, scene of state banquets, the Music Room, where Royals including Prince William have been christened, and the Picture Gallery, home to some of Her Majesty's greatest works of art, a source close to the Royal Household revealed. These currently remain open, but could be closed depending on the results of the survey.
The ceiling problem suggests a growing crisis in the crumbling building. Last night a second Royal source warned the bill for a decade-long programme of repairs - the 're-servicing' of the palace - could be far in excess of the £150 million mooted in June when the Queen's accounts were published.
The source confirmed the palace was in talks with the Treasury about how it could be funded.
Any request for cash from the public purse is likely to ignite a major national debate similar to the one that followed the fire at Windsor Castle in 1992.
A Grade I listed building, Buckingham Palace has 775 rooms, many in desperate need of modernising. Its electrics were installed in 1949 while some areas are still insulated with asbestos and heated by 60-year-old boilers.
Several sections also require reroofing with lead and Welsh slate - it is not unknown for footmen to use buckets to catch rainwater leaking into the palace.
Some areas, such as the ballroom landing pantry, pose a health and safety risk to staff, and the State Rooms, described as "the nucleus of the working palace", have not been redecorated since the Queen came to the throne in 1952.
The closure of the State Dining Room - familiar to millions worldwide as the backdrop to last year's Christmas broadcast - is a blow to the 300-year-old palace, which symbolises the British Monarchy.
It will prompt a serious examination of what must be done to preserve it for future sovereigns. In the short term it means the Queen's annual Diplomatic Reception, a dazzling white-tie event for the country's top 1500 diplomats, will have to be reconfigured without the State Dining Room.
A palace spokesman said: "As the result of a routine survey an issue was found with one of the ceiling beams in the roof space of the State Dining Room.
"Following further assessment, access to the room has been suspended."
The source said: "The State Dining Room is out of service for six months. They are checking the shared roof cavity above six State Rooms."
- Daily Mail