The original Wells Cathedral Clock mechanism is still operating in the Science Museum in London in the Measuring Time Gallery.

The mechanism, which is on loan from the cathedral, is hand-wound each day by curator Richard Horton and members of his team.

He said: "We wind the clock every day at around 8.30am.

"It is wound just enough to keep it going until around 7pm, when it stops.

"It takes around half an hour to complete the whole winding of the three trains."

There is a minute hand to show the movement of time.

The winders have to be careful to wind the clock so that it does not stop in mid-strike.

"There is a rotating fly that spins at quite a rate of knots and you would not want it to start up halfway through a strike," said Mr Horton.

Despite its age, the mechanism now keeps better time than it did when it was in the Cathedral.

Up until the 1880s, when it was removed, the clock lost or gained up to half an hour a day.

These days, it loses hardly any time.

Mr Horton said: "We set it on the hour so it is ready to go at nine o'clock, and start it using the time from a digital clock in the gallery. It loses just a few seconds each day."

The mechanism was dismantled and cleaned last year, and will not need to be taken apart again for another two decades.