Plastic armour

Plastic armour (also known as plastic protection) was a type of vehicle armour originally developed for merchant ships by Edward Terrell of the British Admiralty in 1940. It consisted of small, evenly sized aggregate in a matrix of bitumen. It was typically applied as a casting in situ to existing ship structures in a layer about two inches thick or formed in equally thick sections on a half-inch-thick steel plate for mounting as gun shields and the like. Plastic armour replaced the use of concrete slabs which, although expected to provide protection, were prone to cracking and breaking up when struck by armour-piercing bullets. The armour was highly effective at stopping armour-piercing bullets, because the very hard particles would deflect bullets, which would then lodge between the plastic armour and the steel backing plate. Plastic armour could be applied by pouring it into a cavity formed by the steel backing plate and a temporary wooden form. Production of the armour was by road construction firms in a similar way to road coverings, the organization of the armouring being carried out by naval officers in key ports.

In August 1939, the British Admiralty had considered the possibility that merchant ships might be attacked by aircraft with machine guns and cannon. No armour plate could be spared to protect the ship’s bridges and gun positions so the Admiralty recommended that ship owners fit concrete paving stones in layers up to six inches thick to protect the vulnerable crew. The Admiralty had done no testing with armour-piercing bullets and when the fighting started in earnest, it became evident that concrete armour was almost useless against German machine-gun fire and as the fighting in the English Channel intensified in August 1940, casualties rose and the prospect of a collapse in morale threatened.

Edward Terrell was a successful barrister and magistrate with a flair for invention; by 1940 he had registered a number of patents relating to pens, ink bottles and peeling knives. When war came, he volunteered for the Royal Navy Volunteer Reserve and when he was accepted he was commissioned as a Lieutenant in the Special Branch of the Volunteer Reserve, the highest possible rank permitted by fleet orders under the circumstances.

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