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War on the waterways

Take a look at the connections between war and the waterways, and the impact that war had on the people, places and heritage of our canals and rivers.

Remembrance Day

Less well known than the land girls, the Inland Waterways Women played an important role during wartime. Read more below about how the 'Idle Women' carried vital supplies through our canals and rivers.

Homeland defences and the canals became one and the same thing in wartime. The discovery of air raid shelters in a Smethwick canal embankment serves as reminder of how significant industrial manufacturing was to the war effort, as well as the need for protection in the work place.

Line Blue

Visitors to the Kennet & Avon Canal may have noticed the concrete pillboxes dotted along its banks. These are part of the famous World War II GHQ Line Blue, a defensive stop line constructed to protect Britain against expected invasion in 1940. The threat passed but 75 years later there is still plenty of evidence intact.


Massive concrete pill box remains once inside lock cottage.

Surviving pillboxes have become part of the country's heritage and several of them are now listed structures. Perhaps not quite in the same league as our historic bridges and locks, nevertheless they are a significant reminder that our tranquil canals could have been critical to the freedom of Britain in World War II.

What people may not know is that Line Blue also included all sorts of other defences as well as pillboxes. One of these was the anti-tank ‘hedgehog', used to defend bridge crossings. A series of deep slots were set in concrete below the road surface which could hold vertical steel rails. The rails could be removed to allow local traffic to use the bridge, but when in place they created a a spiky defence to halt an advancing armoured column. Hence the nickname hedgehog.

Ready-made defensive lines

Our waterways provided ready-made defensive ‘stop lines' lines for towns and cities. Fortifications along part of the Grand Union Canal formed a section of the Outer London Defence Ring. Fabricated in reinforced concrete, the pillboxes included embrasures from which soldiers, armed with rifles or light machine guns, could fire on advancing enemy troops.

Troops loading onto a narrowboat

Troops and transport

Mobilising troops during wartime has always been a considerable logistical challenge. Britain's troops were first transported by canal during the Napoleonic Wars and the practice continued through the 20th century.

Although the battles fought through both World Wars were abroad, canals were used to move men and materials around the country.

Evidence of wartime heritage can be found all around. It's often a case of knowing where to look.

Lancashire's canals at war

War-time planners had to consider every eventuality, in particular the likelihood that neutral Ireland could fall under Nazi occupation. The softly shelving beaches of the Lancashire coast, of Pilling Sands on the Fylde, the beaches at Formby and Southport, all with the flat agricultural land behind provided a perfect environment for an invasion.

Therefore, the canals of Lancashire were fortified as stop-lines: the Leeds & Liverpool Canal between Wigan and Liverpool, and the Lancaster Canal north of Garstang up to and including the Glasson Branch. They became anti-tank ditches, their crossings were fortified and other strong points were created. A great deal of physical evidence remains from this time.

Safeguarding London

Canals carried on embankments through low-lying or built up areas such as London were considered vulnerable to aerial attack. If a bomb hit and there was a breach, serious flooding could endanger lives and disrupt strategic resources, vital for the war effort, such as the important transport interchanges at King's Cross and Paddington and centres of manufacturing in the Thames Valley.

In 1938, clause 28 of the Civil Defence Bill (by 1939 the Civil Defence Act) required canal owners to “take measures to secure the due functioning of their undertaking in the event of a hostile attack” with Treasury funding available for schemes completed before September 1939.

Stop planks in London

The ARP department decided to install stop planks and stop gates for the Greater London area and the Slough Arm of the Grand Union Canal. These created sections of canal to minimise the effects of flooding. Stop plank grooves were to be located at the end of aqueducts and all weir sluices. Stop gates were designed, by a Grand Union Canal Company engineer, to be set back into the canal wall so they would not obstruct traffic.

If you'd like to see some ARP stop gates in-situ have a wander around Little Venice and King's Cross near Granary Square. Other gates are located along the Regent's Canal as far as Bow Wharf (don't get confused by the stop gates on the Hertford Union by Old Ford Road Bridge as they are pre-World War II), along the Grand Union Canal as far as Uxbridge and along the Slough Arm.

Our canals now bring wellbeing opportunities to millions of people across England and Wales. For many, part of their enduring attraction lies in the layers of history they continue to represent.

Volunteering outside

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Last Edited: 13 March 2024

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