The anniversary of the famous Dambusters raid on Nazi Germany in the Second World War is being commemorated in Hornchurch on the site of a former wartime RAF base.

The raid by the RAF’s 617 Squadron on the Ruhr Valley 80 years ago this month used the ‘bouncing bomb’ designed by the scientist Sir Barnes Wallis which destroyed two of the massive dams in 1943.

Historian and author Richard Smith is holding a two-day free exhibition at the Ingrebourne Valley Nature Discovery centre in Hornchurch Country Park, in the appropriately-named Squadrons Approach, on May 13 and 14.

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The exhibition, open from 10am to 4pm, features the history of the squadron with memorabilia, photographs and models.

Specially-modified Lancaster bombers led by RAF Wing Commander Guy Gibson attacked the Mohne, Eder and Sorpe dams and managed to breach two of them on the night of May 16-17.

The breach caused floods across the Ruhr Valley that destroyed roads, railways, bridges, factories and farmland.

Enfield Independent: Sir Barnes Wallis designed the 'bouncing bomb'Sir Barnes Wallis designed the 'bouncing bomb' (Image: PA)

But the raid took its toll on the RAF, which lost eight aircraft with 53 crewmen killed.

The 617 Squadron was formed under great secrecy to carry out this strategic raid using Avro Lancaster heavy bombers crewed by airmen from the Canadian, Australian and New Zealand Royal Air forces as well as the RAF.

It had to develop the tactics to use Wallis’s ‘bouncing bomb’ with practice runs over the Upper Derwent Valley dams in Derbyshire which were similar to those in Germany.

The problem was having to fly at just 60ft above the water to drop the spinning bombs at the precisely right angle to hit the surface to bounce before smashing into the dam and exploding.

It was during the practice runs in Derbyshire that 617 Squadron worked out a method to fly at the exact altitude by placing spotlights on each wing pointing down, with their beams meeting exactly at 60ft.

It worked. The ‘bouncing bombs’ hit the surface at the precise angle and skimmed the water to hit the dams.

The rest is history, made into the 1955 Dambusters film of the raid starring Richard Todd and Michael Redgrave which has become a British movie classic.