During the Second World War, London Underground stations were commonly used as air raid shelters, allowing around 170,000 Londoners a night to shelter from bombs on station platforms.

However several Tube stations had some rather unusual uses before they had even been completed, including Wanstead, Gants Hill and Redbridge.

In September 1940, The Blitz on east London caused severe damage to Plessey’s factory in Ley Street, Ilford, which manufactured vital aircraft parts for the RAF.

The factory proposed moving the production line to the tunnels of Underground stations between Leytonstone and Gants Hill, where tunnelling had been completed in 1939, but the stations were not finished.

Plans were approved and work began in 1942 on a secret factory.

Ilford resident Eileen Bunch, 87, who worked in the underground factory when she was 14, has spoken of her role in the factory and its conditions.

She said: “I worked in the factory on the clerical side – I did all the timesheets, worked out how many hours were done and worked out everyone’s wages.

“The only time I ever worked on the machinery was when I was helping the other girls reach their targets.

“It was very normal, everyone was working at that age and most of the jobs at the factory were done by women, as the boys went and joined the forces,” she said.

At its peak, over 2,000 people worked in the underground factory, which was five miles long, 13ft wide and only accessible through the future tube stations.

Overall it produced 8 million shell and bomb cases, an array of aircraft parts for the RAF and 161,500 pieces of electrical equipment.

A railway was built to carry materials to machines along the tunnels and special lighting and air conditioning was installed, as well as a 600-person canteen and toilet facilities for around 1,600 people.

Mrs Bunch said: “It seemed quite normal to me – we just did what we were told. I earned 10 shillings a week which wasn’t very much.

“I also didn’t realise at the time how dirty the conditions were – it really was quite horrible down there.

“If you went to the water tap a rat would just pop up out of nowhere – the rats were everywhere.

“The boys would always play a trick on the girls and go down to the River Roding to kill the rats with a crowbar.

“Then they would come back and hang them over the cages to scare the girls.”

Wanstead station produced devices which intercepted enemy aircraft transmissions, Redbridge tube was where aircraft starter and fuel pump production began and Gants Hill was used to house an automatic machine shop.

All three were eventually opened on December 14 1947 as working tube stations.

John Saville, a former Chadwell Heath resident who attended Wanstead County High School, saw a poster at Wanstead tube station earlier this year about the factory.

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