A huge Second World War air raid shelter lies hidden beneath a well-known Plymouth city centre business, it has been revealed.

The underground bunker apparently measures 18,000 sq ft, according to Larry Speare, and survives in 'mint' condition with its rows and rows of arched corridors, rooms full of bunk beds, toilets and cooking equipment beneath the car park of his carpet and bedding warehouse in Rendle Street.

Larry revealed that the historical treasure was found in 1982 when his current warehouse was being built, but after construction work it was sealed back up and remains as a time capsule from the war.

Now the only sign of its existence below ground is the strangely sloping camber of the tarmac above the vaulted roof.

Larry said: "It's all still there but I would have to dig a hole in the corner of the car park to get back down there."

Larry Speare discovers the hidden air raid shelter
Larry Speare discovers the hidden air raid shelter

Larry remembers: "This was in 1982. We had to get a huge test drill in to check before we sank the foundations.

"They were drilling through concrete and all of a sudden they couldn't work out why they were going through the ground with such ease. There was just a top crust and then nothing.

"There was a lot of consternation in case there were tunnels underneath and we had to get a digger.

"It turned out that by coincidence they had actually dug down at the same spot as the entrance steps, in the corner of our car park.

"There were steps going down and they were painted white. Even after all those years 40 years after the end of the war the paint was bright white and it was almost in mint condition.

"It was strange going down inside. There was great excitement about what we would find.

The car park curves over the roof of the hidden air raid shelter below

"The Air Raid Shelter covered the entire area of the car park - I was told that the dimensions were 18,000sq metres - it stretches from the front gate to the rear wall.

"There was the one entrance that we found and two exits at the back. Obviously it was put there to protect lives because of the Blitz and the heavy bombing in the centre of Plymouth. There were all those people who died at the air raid shelter in Portland Square.

The Portland Square air raid shelter, which has now been built upon, was always thought to have been destroyed in the Blitz, but was found intact around 12 years ago.

Back in 2006 part of the remains of the World War II Portland Square air raid shelter was rediscovered on the campus of Plymouth University.

The shelter saw the largest single loss of civilian life in the city when at least 76 civilians were killed, including a mother and her six children, as the underground shelter took a direct hit from a German bomb on the night of April 22, 1941, at the height of the Blitz

Inside an air rail shelter in Plymouth

Paul Diamond, founder of Hidden Heritage, said previously: "I've documented around 30 shelters in the Plymouth area so far. I'd say there are around 20 left."

He described what it would have been like for those hiding in the shelters: "You would've heard the drone of the bombers - explosions left, right, and centre.

"Even before it got hit there would have been earlier raids and this was one of the most heavily targeted areas in Plymouth. It would have been terrifying.

"Quite a few did take direct hits; Portland Square, Marlborough Street, Charles Cross, Inverdene.

"When word got out, people were scared enough to come into these shelters to begin with, but they actually started refusing - they would hide under their staircases instead."

It was not until 1945 that Plymouth was able to say goodbye to the shelters for good and return to some kind of normality in the fire-scorched, flattened remains of the city above.

Do you remember relatives talking about the Rendle Street air raid shelter in the 1940s?  Contact news@Plymouthherald.co.uk