The bell used in the opening ceremony of the London 2012 Olympic Games, where it was rung by Sir Bradley Wiggins, is the largest harmonically-tuned bell in the world.
It is 2m high, 3.34m in circumference at the base and weighs 23 tonnes. It is 30cm wider than the previous largest bell in the UK, the Great Paul of St. Paul's Cathedral. Its main tone is tuned to the B note and as such has the lowest tone of any bell in the world.
It was designed and tuned by the Whitechapel Bell Foundry, but the foundry furnace only has a capacity of eight tonnes, so it had to be cast in the Netherlands at the Royal Eijsbouts foundry.
It was designed to be as large as possible, but was restricted by the requirement for it to fit through the athletes' tunnel in the Olympic Stadium, something it managed with only a few inches to spare.
The bell is inscribed with "London 2012" and the line from The Tempest that was spoken during the ceremony by Kenneth Branagh, "Be not afeared, the isle is full of noises".
It is due to be returned to the Whitechapel Bell Foundry in 2212 for re-tuning. [UPDATE: That was the original plan, but the Whitechapel Bell Foundry permanently closed in May 2017]
 The Whitechapel Bell Foundry has existed since 1570 and has manufactured many famous bells, including Big Ben and The Liberty Bell.