MUD, shells and barnacles from 68 years under water are being scraped off a Second World War bomb.

The Nazi rocket, which narrowly missed flattening Harwich in 1944, is kept at the town’s Redoubt Fort.

The rocket landed harmlessly in the Harwich Harbour, witnessed by 16-year-old fisherman Reuben Day, who described the sound as “like a tube train going through the air”.

The remains of Hitler’s V2 – which travelled at four times the speed of sound – were only rediscovered in March 2012.

Harwich was put on red alert and an exclusion zone set up as Royal Navy bomb disposal experts tried to find out if the two-tonne missile was dangerous.

Astonishingly, sailors and fishermen had been mooring their boats to the wreckage for years without realising what it was.

Fortunately, its deadly warhead was missing, and after a delicate retrieval, the engine section now has pride of place at the Harwich Society’s Redoubt Fort.

But 72 years in the sea has taken its toll.

John Theobald, Harwich Society volunteer, said: “We had a gentleman in to the fort last year who had just started his apprentice at the Shotley side when this rocket exploded in the air - it malfunctioned in the air.

“It was reviewed at the time, but stayed there from 1944 until 2012.

“It has a lot of corrosion from salt.

“We are trying to clean it and stabilise it so it doesn’t rot away any more.

“It had mud and barnacles and oyster shells on it - it was in the water getting all the marine life, mud and clay that washes down the Stour.

“That is quite difficult to remove, something like sandblasting would destroy the corroded metal.

“Don Hambling, who is doing the work, is cleaning it and painting on a rust cure.”

It is hoped the rocket engine will then be displayed on its side on a special frame with a roof.