London's emblematic Big Ben clock will ring for three minutes to celebrate the first day of the Olympic Games on Friday, organisers said, the first time it has rung outside its regular hours since the funeral of King George VI in 1952.
Thousands of bells across Britain, from the Shetland Islands north of Scotland to the UK's most westerly church in Cornwall, will join in.
Big Ben will chime 42 times between 8:12 (0712 GMT) and 8:15 a.m. on July 27, after special permission was granted by parliament for the bell to toll out of its regular schedule.
The occasion will be a live performance as the bells will need to rung by hand, said Keeper of the Great Clock Mike McCann in a statement.
"We need to manually lift the brake that controls the weight that drives the mechanism that strikes Big Ben," he added.
The bells at the National Assembly for Wales, Stormont in Northern Ireland and the Scottish Parliament in Edinburgh will also ring at 8:12 a.m.
"It is a sign of how special this summer is when one of the world's most famous bells will ring outside its regular schedule so it can be part of this London 2012 Festival commission to ring in the Olympic Games" said House of Commons Speaker John Bercow.
The three-minute chime will be broadcast to TV, radio and online audiences with more than 10 million listeners expected to tune in, according to estimates.
Thousands of participants have already signed up to join in, including the Royal Navy, the Mayor of London and the famous Whitechapel Bell Foundry in east London.
The chiming sequence, entitled "All The Bells," will form part of an event devised by musician Martin Creed.