Genius in its simplicity
THE canal lock is a masterpiece of simplicity that ingeniously carries boats uphill and downhill in still water. It’s the place gongoozlers gather and where passing boats cram conversations and camaraderie as they wait for their boats to be lifted from one water level to another. The ordinary lock is the humble showpiece of Britain’s entire canal system. Without it, canals wouldn’t work.
Any canal journey would have ended at the first incline, since without nature’s tides or currents, the water in man-made canals wouldn’t allow canal boats to travel up or downhill without help. A lock is a man-made chamber with wooden or steel gates at either end. In canal terms, it creates the ‘pound’ between a canal that is split on a slope, at two flat levels.
A boat that wants to travel uphill through a lock must empty the water from the chamber to match the level of the lower canal. The bottom gates can then be opened, and the boat enters the chamber. By using a windlass to turn the top paddle, a sluice gate opens and allows water to fill the chamber from the upper canal.
The gates are held shut by the pressure of water, and it is only when the level reaches the same height as the upper canal that the top gate can be opened, and the boat can carry on its journey. A boat wanting to travel downhill follows the same process in reverse.
The working lock has no need for improvement, its simplicity is its joy, and everyone who sets off on a canal journey today becomes a time traveller, working the locks in the same way as they would have functioned over 200 years ago.
But the canal lock has older roots than 19th-century Britain. It is believed that Chhiao Wei-Yo invented the pound lock in AD983, with the first recorded lock built on China’s Grand Canal in AD984. Two water gates were built 250ft apart to create a temporary alteration in the water levels.
Italy is recorded to have been the first to introduce the true pound lock in 1373, a century before Britain dabbled with the idea. And with its vertical gates and pioneering spirit, the Exeter Ship Canal was responsible for the first pound lock in Britain. The mitre lock with its familiar V-shaped gates which are held together by the physics of water dates back to Leonardo da Vinci (1452-1519). Britain’s first mitre lock was on the River Lee at Waltham Abbey.
The ordinary lock is historic, but if history implies something past, the canal lock is much more than that. Canals keep reinventing themselves, with new water travellers arriving with every era. From traditional 19th-century working boats, to the Idle Women doing their bit for the Second World War, and from the pioneering leisure boaters of post-war times to the canal mania of recent years: the humble lock has served them all.
Its function is the undeniable triumph of Britain’s canal networks, yet more unquantifiably the visual dynamics of entire canalscapes owe everything to the lock. The vision of great outstretched arms that are coated in the distinctive, and oddly romantic, black and white colours of the Canal & River Trust does more than anything else to pump the adrenalin of a view.
Some folk might head off to sightsee the biggest lock flight in the most spectacular scenery, others may simply saunter to their local canal, but everyone inevitably ends up standing and staring, trying to unravel the unfathomable mystery, ‘how does a lock work?’
There are two different types of single locks. The broad lock can hold wider boats or can fit two narrowboats side by side, and the narrow lock can only fit one narrowboat at a time. Some of the wonders of the waterways come from individual locks being joined together as a long flight or a steep staircase – or when they appear in unusual locations, opening into the sea, or are built to be extra deep or wide due to the terrain.
The longest lock flight in Britain is at Tardebigge on the Worcester & Birmingham Canal, the deepest lock is Tuel Lane Lock at Sowerby Bridge on the Rochdale Canal, the steepest staircase of locks is Bingley Five Rise on the Leeds & Liverpool Canal, and the longest staircase is the Caen Hill Flight at Devizes on the Kennet & Avon Canal.
As locks are of special historic interest, many locks or lock flights along the canal network are now Grade I or Grade II listed.
On canals throughout Britain. The canals are open all day every day – just find your local canal.
How to get there
National Rail Enquiries 08457 484950
Traveline 0871 200 2233
Canal towpaths are now easy routes to cycle and walk, many being part of Sustrans National Cycle Network or long-distance walking trails.
There are plenty of visitor moorings available along Britain’s canals.
Local Tourist info
Canal & River Trust/Glandwr Cymru
Use the Canal & River Trust website to find specific local canal information.
Words: Phillippa Greenwood
Images: Martine O’Callaghan