The device dubbed the most crucial timepiece globally once brought Del Boy wealth – yet its actual creator assisted in preserving numerous lives at sea.
The individual responsible for that timepiece was John Harrison, a self-taught clockmaker whose precise marine chronometers revolutionized navigation.
Harrison died 250 years ago, in 1776, on his 83rd birthday, and was buried in the Hampstead Parish Churchyard.
John Harrison’s grave – the lifesaving marine clock inventor – is located at St John’s Churchyard in Hampstead.
However, he is remembered as the man who solved the centuries-old problem of calculating longitude at sea, an achievement that enabled sailors to determine their east-west position.
His invention – resembling a large pocket watch – won him a competition and made ocean voyages safer.
Harrison’s legacy was featured in a 1996 Only Fools and Horses episode titled Time on Our Hands, in which Del Boy and Rodney Trotter discover a Harrison chronometer in their storage room and sell it at auction, becoming millionaires.
The cast included Raquel Turner played by Tessa Peake-Jones, Del Boy Trotter played by David Jason, Rodney Trotter played by Nicholas Lyndhurst, and Cassandra Parry played by Gwyneth Strong.
Beyond the TV appearance, Harrison’s chronometer solved a problem that had caused countless ships and thousands of lives to be lost at sea.
In the 18th century, determining longitude at sea became a national obsession.
The urgency of the problem was tragically highlighted in October 1707, when four Royal Navy ships – HMS Association, HMS Romney, HMS Eagle, and HMS Firebrand – were wrecked on the rocks of the Scilly Isles because they couldn’t determine their position.
At least 1,400 lives were lost, including the national hero Admiral Sir Cloudesley Shovell.
The disaster prompted Parliament to offer a reward of 20,000 pounds – approximately 3.5 million pounds in today’s money – for anyone who could design a reliable and accurate marine chronometer for use at sea.
Seafarers needed to know the precise time at a fixed reference point to calculate their exact position at sea. Even tiny errors could be catastrophic.
Harrison, born in Yorkshire to a carpenter father, realized that the key was a clock accurate enough to keep the time of a reference location like Greenwich, while withstanding the humidity, air pressure, and temperature changes of sea voyages.
He spent decades researching the problem that had baffled the greatest minds of his time, constantly refining his designs through painstaking trial and error.
In 1735, he completed his first marine chronometer, called H1; by 1759, he had developed H4, a pocket watch that met the requirements of the Longitude Act and kept accurate time even on ships.
However, Harrison had a stubborn, cantankerous nature and made enemies among the members of the Board.
They awarded him only half the prize money, and it was only after his son William appealed directly to the king that he received the rest.
Harrison’s legacy extended far beyond the marine chronometer.
He also invented the bimetallic strip to compensate for temperature changes on ships – a technology now used in thermostats, fire sprinklers, and even kettles.
Additionally, the caged roller bearings used to withstand the motion of ships are essential components in modern machinery.
Some historians consider H4 to be the most important timepiece in the world. It is now displayed at the Royal Observatory in Greenwich, near the Prime Meridian – a line that exists because of Harrison’s contributions to navigation.
His remarkable life is commemorated by his gravestone at St John’s Church, a plaque in Westminster Abbey, and a memorial on his former home at Red Lion Square in Holborn.