Big clocks

In 1671, the old clock at King's College Cambridge was scrapped and a new one ordered from William Clement of London at a cost of £40. A turret was built to house the clock on the North side of the College chapel.

The mechanism produced by Clement had a pendulum nearly 2 metres long, which made 47¼ half-swings every minute. It was one of the earliest pendulum clocks and could have been the first clock built with an anchor escapement and a long pendulum. Initially, the clock had only one hand. Minute hands were rarely seen on turret clocks before 1700.

A pendulum keeps time best if its angle of swing is small. With an anchor escapement, a larger angle is not needed so Clement was able to use a long pendulum swinging through a smaller angle.

In 1817, the College authorities decided that the clock's usefulness had come to an end and it was taken down. After two years, nobody had agreed to buy the old clock so it was given to St. Giles' church which was being extended. The clock was extensively modified by Thomas Safford, who gave it a minute hand, changed the layout of the wheels and replaced the old wooden barrels around which the ropes were wound. The only reason why the clock was not scrapped and completely replaced was because its frame was well made and frames of that kind were still being used. The design of turret clocks changed little until Lord Grimthorpe introduced the horizontal frame for the Westminster clock in 1854. The altered clock was installed above the door of the enlarged church in 1823 and was the only public clock in the area.

In 1876, the church was pulled down because the previous building work had made it unsuitable for services. An impressive new church was planned, with a tower for the clock and bells. Unfortunately, money ran out before the tower could be built so the clock had to be installed in a gable. In 1925, the mechanism stopped working properly and was again going to be scrapped until The Director of the Cambridge University Museum of Archaeology recommended that it should be given to the Science Museum.

The clock at St. Giles' was made to work again in 1955, this time with an electric motor.