Operation London Bridge (also known by its code phrase London Bridge is Down) is the name of a funeral plan for Queen Elizabeth II.
The plan includes the announcement of her death, the period of official mourning, and the details of her state funeral. The plan was first created in the 1960s and revised many times in the years before her death in 2022.
The phrase "London Bridge is down" would be used to communicate the death of the Queen to the prime minister of the United Kingdom and key personnel, setting the plan into motion.
Bodies involved in preparing the plan included various government departments, the Church of England, Metropolitan Police Service, the British Armed Forces, the media, the Royal Parks, London boroughs, the Greater London Authority and Transport for London. Some critical decisions relating to the plan were made by the Queen herself, while some were left to be determined by her successor.
Reporting on the preparations, The Guardian described them as "planned to the minute" with "arcane and highly specific" details.
As well as Operation London Bridge, there is an additional plan called Operation Unicorn, which details what would happen if the Queen were to die in Scotland. Running concurrently with Operation London Bridge is Operation Spring Tide, which addresses the accession of King Charles III to the throne and his first trip to the countries of the UK.
Several Commonwealth realms developed their own plans for how to react to the death of the Queen.