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 essentially consisted of small, evenly sized rock or stones in a matrix of bitumen. It was typically applied as a casting in situ to existing ship structure in a layer of about two inches thick or formed in equally thick sections on a half inch thick steelplate for mounting as gun shields and similar.

It 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. Plastic armour was highly effective at stopping armour piercing bullets because the very hard particles would deflect the bullet which would then lodge between 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 officiers in key ports.