The rehearsal, given the code name 'Castle Dove' according to Express,saw officials discuss the day immediately after the monarch passes.
This occasion marks the first time civil servants and politicians came together to discuss the plan, which would also involve the Prime Minister addressing a nation in mourning.
Though the rehearsal is not in response to any fears about Her Majesty's direct health, the protocol was done at an 'unprecedented' scale.
A source told The Sunday Times, 'This is the first time different ministers have come together in one room. Previously it has only been officials.'
A cabinet minister added: 'Things have clearly been stepped up because of the ageing process.'
Her Royal Highness underwent surgery last month to remove a cataract from her eye, Buckingham Palace announced earlier.
Her Majesty 'successfully underwent a short planned procedure', a spokesman from the palace said.
The Queen still plans to attend all scheduled engagements.
This article originally appeared on New Idea.