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From toys to Sten

triang toys

The outbreak of war in 1939 required manufacturing companies to stop making peacetime goods like children’s toys and start churning out deadly weapons and ammunition. One of these firms was Lines Brothers, based in Merton in south-west London. Lines Bros was better known under its tradename ‘Tri-ang’, named for the three sides of a triangle and the three founding brothers Walter, William and Arthur Lines. Some readers will remember the ‘Tri-ang’ range of colourful sheet metal toy cars, trucks, and other vehicles. Successive generations grew up playing with these toys from their launch in 1919 until well after 1971 when the company ceased trading. Today the toys are collectors’ items.

By 1939 Lines had one of the largest and most modern factories in the world, which made it a prime candidate to be repurposed by the British government for war work. Lines started taking on contracts for small arms ammunition, artillery shell fuzes, and parts for weapons. In 1941 Walter Lines offered to do more than just make parts of weapons. As well as a capable factory, Lines’ company were specialists in making things out of ‘pressed’ sheets of steel. Walter proposed a new version of the Sten submachine gun that made extensive use of sheet steel. Lines himself redesigned the already cheap Sten to suit the machinery and processes used in his factory, reducing manufacturing time down to just 5 ½ hours per gun. The War Office approved the design as the Sten Mark III. This differed from the better-known Mark II in several ways. Its sheet metal body was longer, extending out along the barrel and replacing the separate hand guard of the Mark II. The sheet metal construction resulted in a long distinctive rib along the top of the gun where the two ends of the sheet were welded together. The Mk. II magazine housing, designed to rotate for storage, was replaced by a simpler welded-on version. Because the barrel was permanently welded into the body, the barrel could not be replaced when it wore out – this was a truly disposable gun and so less cost-effective in the long run. The gun could also no longer be fitted with a bayonet, although these were rarely used anyway.

Second World War Sten gun without magazine

Centrefire automatic submachine gun – Sten Mk.III (about 1943-1944) Late pattern model, British. PR.7575

The new Sten was put into production in Spring 1942, and an initial contract of 500,000 guns was completed on time only by employing three shifts of workers on 24 hour per day production. As they did in other arms factories, many women worked in the critical roles of welding and final hand assembly of the guns, whilst men with prior manufacturing experience (and in a reserved occupation) tended to set up and operate the machine tools that made the individual components. Another 500,000 gun contract was won from the government as a result. Unfortunately the adaptation to stamped steel was not without problems. This was hardly surprising given the record time in which Lines were turning out a product that they had never before made. Still, a delicate balance of cost, speed, and effectiveness was being attempted, and more defects were found with Mark IIIs than the Mark II. As the need for guns was easing, with production of Mk. II guns now sufficient in other factories, the decision was taken to cut the second contract short. Minimising the chance of additional reliability problems in the field (the Mark II was hardly the most dependable gun as it was), Mark IIIs were prioritised for issue to the Home Guard. In Home Guard service the guns would be shielded from the sand, mud and hard service of frontline combat. Despite this, Mk. III guns did see widespread foreign service, and were also dropped to partisan fighters in Europe. When production ceased in Autumn 1943, an astonishing 876,886 had been made at Merton. Walter Lines and his company had made a significant contribution to the nation’s defence – just as they did to its collective childhood.

You can see an example of the Mark III Sten alongside its tinplate toy forerunner in our permanent War Gallery display ‘Firefight: Second World War’.

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