HISTORIANS and archaeologists have been left fascinated and perplexed by a unique Second World War relic in Shooters Hill that might have been a secret command centre for UK forces.

The area was an important defensive outpost for the Home Guard and was the focus of a recent Time Team investigation for Channel 4.

But the TV archaeologists were unable to unravel the mystery of a large and elaborate underground air raid shelter that spreads across two back gardens in Ashridge Crescent, disguised on both sides by rockery.

Responses to the Time Team programme have helped shed some light on the structure's use, but local experts still do not know whether it was a private shelter or one used for official reasons - such as a communication centre for the Home Guard.

Shooters Hill archaeologist Andy Brockman said: "This shelter has lighting and electricity power points, which we know were there during the war because they are actually built into the concrete.

"To have an air raid shelter built underground from concrete, on domestic premises, with quite so many facilities, is unprecedented. It's much more substantial than you would expect, so there is a real mystery here and one that we are hoping to get to the bottom of, because we think there is a very interesting story to be told."

Both the adjoining gardens have a set of hidden steps that lead down to the shelter, which consists of two rooms, both about 10ft by 10ft.

The Time Team programme said it might have been built as a clandestine base for Home Guard guerrilla cells, but a letter received after the programme aired suggested otherwise.

Sian Reeve, who now lives in Suffolk, grew up in one of the houses in the late 60s and 70s. She claims her family bought the house from a man called Mr Griffiths, who had built the shelter with his next door neighbour, Mr Cuffley.

She said Mr Cuffley worked for the electricity board and Mr Griffiths owned a "demolition company", and that they built the shelter simply to keep their families safe. But Andy thinks there might be more to the story.

He said: "We know the names are right and they were both living there during the war, because we have checked the electoral register.

"Logistically they would have had the know-how and, presumably, access to the equipment to build it, but this thing is built of very thick concrete, which was in short supply and strictly rationed at the beginning of the war, so we don't know how they managed to get hold of so much.

"It's possible they were siphoning off resources to protect their families, but there's also a chance that this was just a cover story for a secret official function."

Andy is now asking the public to come forward with information that could help the experts solve this mystery. He said: "Does anyone remember the Cuffley and Griffiths families in Ashridge Crescent, particularly during the pre-war and wartime years? What were their jobs? Were they involved in the Home Guard or Air Raid Precaution Service? In particular, does anyone remember the air raid shelter in the garden?"