BORIS Johnson's plans for an airport in the Thames Estuary could trigger an explosion and tsunami which would engulf large parts of Dartford and Gravesham, if an expert is to be believed.

The Government is expected to publish its consultation into increasing the UK’s airport capacity in March, with two proposals zeroing in on the coast near Gravesend.

But the presence of the SS Richard Montgomery - which sank off the north of Sheppey in 1944 and contains 1,400 tonnes of unexploded bombs - could scupper the plans.

Despite being under water for more than 67 years, the explosives inside have not degraded and one expert says an explosion would wreak havoc and even trigger a tidal wave.

Colin Harvey has made a documentary about the Montgomery called The Wreck and has appeared on TV and radio around the world to talk about it.

He said: “Would you build an airport knowing there are 1,400 tonnes of bombs at the end of the runway?”

The 67-year-old says a risk assessment officer who studied the ship told him of the disastrous consequences.

Mr Harvey added: “Three hundred bombs on 1,000 troops would wipe them out. There are 2,000 on the ship. They are all armed - that’s the most damning thing.

“If you have got a high tide, you will have a 360-degree tsunami because of the force of the bombs. It will be enormous.

“In Dartford and Gravesend you would get a wave for sure.

“At low tide, you would have a big blast, which would have a disastrous effect. You would hear it in London.

Semi-retired electrician Ron Angel, who runs the website ssrichardmontgomery.com, said: “Building work nearby or vibrations on the sea bed or aircraft flying close all adds to the risk of something happening.”

The wreck is observed 24 hours a day by radar and protected by an exclusion zone and has adopted a policy of non-intervention because it says it is safest to leave it alone.

A Department for Transport spokesman said: “It is too soon to say whether the SS Richard Montgomery would have any bearing on the future of the UK’s aviation policy.”

However, the director of coastal and maritime at Wessex Archaeology, Euan McNeill, said: “I do not see the Richard Montgomery as a showstopper for a major development.”

The Montgomery

The SS Richard Montgomery was waiting to join a convoy to Cherbourg when it ran aground off the coast of Sheppey on August 20, 1944.

Sailors desperately worked to remove the 8,687 tonnes on board but it was left with more than 1,400 - including 2,000 cases of fused and non-fused cluster bombs, nearly six hundred 500lb and 1,000 1,000lb bombs that will not deteriorate.

The ship is surveyed every year by the Maritime and Coastguard Agency and the most recent report, published in September noted ‘slow but continual deterioration’ which could lead to its cargo leaking out - the results of which could not be predicted.

A study published by the Southend-on-Sea and District Chamber of Trade and Industry back in 1972 said: “It is almost certain that the detonation of any of these bombs will set off the remainder.”

It added: “We can only conclude that the nearby centres of population are exposed to a serious explosive hazard which will continue undiminished as long as the bombs remain.”