text: 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 Martin Burgess Clock B 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 Martin Burgess Clock B (left), which is based on a design by carpenter John Harrison (right) from 300 years ago, has stunned experts by keeping accurate to a second for 100 days . 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 Independent on Sunday reported. 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,' Mr Betts added. The modern-day clock has since been certified by the Guinness World Records, which the National Maritime Museum confirmed on Twitter . The Martin Burgess B clock has been part of a 100-day trial at the Royal Observatory (above), 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 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 died in 1776. He has since been the subject of Dava Sobel's bestselling book Longitude, as well as a film with the same name starring Michael Gambon (right) and Jeremy Irons (left) John Harrison was a carpenter born in 1693 in Lincolnshire. In the early 18th century a lot of Royal Navy ships were being lost at sea. Although latitude was relatively easy to determine using the sun, longitude was harder. The problem was considered so important Parliament offered financial rewards of up to £20,000 to anyone who solved it. Clockmakers argued that a heavy pendulum bob and short swing would be the best. But Harrison dismissed this theory and thought a clock with a lighter pendulum bob and wide swing would work better. He designed his first clock in 1713 aged 20. His 'longitude' clock, which was the basis of the Martin Burgess Clock B, would solve the problem of determining longitude at sea, he claimed. By knowing the amount of time the ship had been at sea and the local time by using the sun, sailors would be able to determine longitude accurately. Local time is one hour ahead for every 15 degrees of longitude east and one hour behind for every 15 degrees of longitude west. He was not taken seriously by any of his contemporaries and the possibilities of his clock were not explored until the 20th century. Harrison died in 1776. He has since been the subject of Dava Sobel's bestselling book Longitude, as well as a film with the same name starring Michael Gambon and Jeremy Irons.
target: Martin Burgess Clock B is based on John Harrison's 18th century design .
  Clock was strapped to a pillar at the Royal Observatory in Greenwich .
  Time measured using a radio-controlled clock and the BT speaking clock .
  Certified by Guinness Book of Records, National Maritime Museum said .