Bells have been cast at the Whitechapel Bell Foundry in east London for more than 400 years.
Big Ben was cast here in 1858 - at over 13 tons, the largest bell it ever produced. The Liberty Bell in Philadelphia was also cast here more than 250 years ago.
After being cast, bells need tuning in order to sound good and to match the others in a set or "ring".
Whitechapel Foundry's Head Tuner Nigel Taylor explains how he makes a new bell get its best possible sound.