Scuba divers who raised a rare wartime 'bouncing bomb' from the depths of a lake are dropping in at the Hertfordshire museum where it is now a star exhibit.

The team of 20 will be at the de Havilland Aircraft Museum at Salisbury Hall, London Colney, on Sunday, October 24.

There they will get their first proper look at the inert practice half-ton bomb they gave to the museum and which has now been cleaned and preserved.

Herts Advertiser: Highball in its tank being refilled with a special anti-corrosion solution.Highball in its tank being refilled with a special anti-corrosion solution. (Image: DHAM)

The divers will meet the restoration team of volunteers looking after the museum’s three World War Two de Havilland Mosquito fighter-bombers, variants of which had been tasked with dropping the bomb on anti-shipping strikes against the Japanese Navy in 1944.

Museum general manager Jonathan Fulwell said: “It is an incredible bomb and we are delighted to welcome the divers and show them what we have done with their unique gift.”

Herts Advertiser: The Highball bomb arrives at the de Havilland Aircraft Museum in 2017 watched by some visitors.The Highball bomb arrives at the de Havilland Aircraft Museum in 2017 watched by some visitors. (Image: DHAM)

Visitors to the museum this Sunday will be able to join the Mosquito team at a special presentation to be given by the divers from the East Cheshire branch of the British Sub Aqua Club to show how the recovery operation was carried out.

More than 200 of the practice bombs had been dropped by the Royal Air Force against a target on Loch Striven in Scotland.

Herts Advertiser: A BSAC diver spotlights the Highball on the loch bed.A BSAC diver spotlights the Highball on the loch bed. (Image: Lindsay Brown, BSAC)

The diving team spent seven years locating the bombs and deciding how to raise them.

Having found them, in 2017 they decided to ask the Royal Navy for help in getting one of them up.

Their efforts were so successful that with the use of a Navy floating crane they raised two of the inert practice bombs, which had lain at a depth of 120ft for more than 70 years. Navy divers also raised one.

Herts Advertiser: The Highball being raised by the Royal Navy ship.The Highball being raised by the Royal Navy ship. (Image: Henry Paisey, BSAC)

It was the first time anyone had seen one of the bombs since 1945, and corrosion was already affecting the metal casings.

The loch had been used by the RAF as a bombing range where the bombers could get a lot of practice at dropping the spherical bombs, named Highball.

These were versions of the cylindrical bouncing bomb codenamed Upkeep used by the RAF’s 617 ‘Dambusters’ Squadron in 1943 and also invented by Barnes Wallis.

Herts Advertiser: The Highball safely on the deck of the ship.The Highball safely on the deck of the ship. (Image: Henry Paisey, BSAC)

As a practice target, two old Royal Navy battleships were anchored in the loch and the bomb the team gave to the museum bears the large dent made when it actually hit one of them.

“Realising that it had hit the target made their donation that much more appreciated,” said Mr Fulwell.

“It was a considerable achievement to recover the bombs, and to keep it in context we have now positioned it under the bomb bay of one of our Mosquitos.”

Herts Advertiser: The Highball bomb restored and now under the DH Mosquito B Mark 35 at the de Havilland Aircraft Museum.The Highball bomb restored and now under the DH Mosquito B Mark 35 at the de Havilland Aircraft Museum. (Image: DHAM)

He added: “The Highball was designed to be dropped by de Havilland Mosquitos with modified bomb bays and as our museum has three of these aircraft, we were more than delighted to be asked if we would like to have it.”

Of the Highballs raised, the team also gave one to the Brooklands Museum in Surrey.

For more information about the volunteer-run museum visit www.dehavillandmuseum.co.uk