IT is one of the most famous episodes of the Second World War thanks to the genius of designer Barnes Wallis, the bravery of 617 Squadron and of course the 1950s' movie with its stirring theme tune.

What is less well known is that the bouncing bombs dropped from those legendary Dambuster raids were tested in a series of secret operations on a Scottish loch.

The tests were carried out on Loch Striven, which is on the Glenstriven estate in Argyll, with locals being evacuated from the area so they would not know what was going on.

Now the estate, which has been owned by the Blacker family for the last 30 years, has been put up for sale.

The Blackers bought Glenstriven in 1981 when it was in a dilapidated state and turned it into a large commercial estate known for shooting and sailing.

Speaking from South Africa yesterday, the head of the family, Peter Blacker, said over the years the estate had become more a business and less a family home and the time had come to sell.

Mr Blacker said he had always been aware of the estate’s connection to one of the most important chapters in the history of the Second World War.

Last summer, a team from Dundee University visited the estate and found 14 test bombs still lying at the bottom of the loch. There are also still black marks on the rocks by the loch from the tar burned to create a smokescreen to hide the tests.

A member of the Berry family, who owned the estate at the time of the tests and were the only people allowed to stay in the area, told Mr Blacker of the secrecy surrounding the operation.

He said: “The security people came into the main house at Glenstriven and moved all the family to the back of the house, shut the curtains and the bombers would come down the loch.”

Loch Striven was chosen because the landscape resembled the area of Germany where the bombs were to be dropped. The practice bombs were made from concrete and aimed at an old ship in the middle of the loch.

After the success of the tests, the bombs were used in the famous Dambuster attacks in Germany.

Two dams were destroyed by the RAF’s 617 Squadron in Operation Chastise in one night in 1943.

This summer, the team from Dundee University plans to return to Glenstriven and try to recover the sunken bombs. Mr Blacker has been promised one as a souvenir.

He decided to sell after his use of the estate started to fall. He said: “There was a big programme to develop the neighbouring estate, Knockdow, which we sold last year. It was going to become a resort destination, spa, golf, etc, and the idea was that the commercial shoot guests from Loch Striven would be staying down at Knockdow.

“But things change in people’s lives and the estate hasn’t been used enough.”

“It’s been a huge project and every year a project’s been going on, but it’s got to the end now.”

Mr Blacker said the estate of around 5000 acres was a very special place and named his favourite spot on the estate as the summit of Leacann nan Gall which has views to Glasgow.

There are nine properties on the estate including the main house, which has eight bedrooms and three reception rooms. Four of the houses are let to tenants while the others are holiday lets.

The estate is up for sale as a whole or in up to eight lots. Prices range from offers over £235,000 to £2,500,000 and the property is being sold by Edinburgh agents John Clegg & Company.