300-yr-old clock design proves as accurate as chronometers!

A clock based on a design from 300 years ago has stunned experts by keeping accurate to a second for 100 days.

The modern-day recreation of the clock, named Martin Burgess Clock B after its modern re-creator, is based on John Harrison's 18th century clock, which he thought up to solve the problem of determining longitude at sea.

It has been part of a 100-day trial at the Royal Observatory, in Greenwich, to see if the claim - that the clock would neither lose nor gain more than a second in 100 days - was true.

The clock, which was built using modern materials, was initially set ticking a year ago after being strapped to one of the Observatory's supporting pillars.

But it quickly became apparent the trial would be a success and wax seals were placed on its case so its accuracy could be verified.

The time was measured using a radio-controlled clock, which received the national time signal, and the BT speaking clock.

Jonathan Betts, a member of the Antiquarian Horological Society, said, ''As soon as we set the clock running it was clear that it was performing incredibly well, so then we got the case sealed because nobody was going to believe how well the clock was running.''

He added that the clock was not a replica of Harrison's, but used his design and concept.

''It is important to realise his design goes against everything the establishment has claimed is the best throughout history,'' Betts added.

The clock has since been certified by the Guinness World Records. When it was measured it was reading UTC time to within a quarter of a second.

The National Maritime Museum confirmed the record on Twitter yesterday. It wrote: ''Our 100 day trail of "Clock B" won @GWR for 'most accurate mechanical clock with a pendulum swinging in free air'!''

Rory McEvoy, the Observatory's curator of horology, added, ''What we've seen here is something approaching a perfect clock, but we are not there yet.''

Harrison, who was the subject of Dava Sobell's bestselling book Longitude (1995), which told the story of his solving of the problem of determining longitude at sea, had boasted that his latest pendulum clock would neither lose nor gain more than a second in 100 days. Last Thursday morning his claim was shown to be as accurate as the timepiece he had designed.

In his later years, Harrison had left instructions on how to build the clock in an obscure book, which was so hard to read it became known as ''the ramblings of superannuated dotage'' by later horologists.

''It was a claim that Harrison made and a claim nobody believed because the best clocks of the day couldn't do better than about a second a week, if they were lucky,'' Betts said. ''So the idea that somebody was going to keep time to an accuracy of a second in 100 days was preposterous. It was only in the 20th century that people thought that Harrison may have been right.''