A Second World War bomb ship has threatened to cause a 'Thames tsunami' for the last 80 years, according to national press.

But how serious is the risk? Joe Crossley reports.

This week 80 years ago the American cargo ship SS Richard Montgomery sunk 1.5 miles off of Sheerness.

The boat, named after an American hero of the War of Independence against Britain who was killed while attacking British Quebec in 1775, had been set to join a convoy heading to Cherbourg in France after docking at Sheerness. Instead, it ran aground and broke in half.

It headed to the bottom of the sea carrying 7,000 tonnes of ammunition. Roughly half were salvaged but around 14,571 bombs remain in the shipwreck.

This pay-load, and the potential of it going off unexpectedly, has captured the imagination of both the locals living on Sheppey and the national media.

A government test was conducted in 1970, which detailed the worst-case scenario or ‘top event’ if the entire cargo of bombs exploded. This seemed to create the myth of ‘The Monty’.

According to the report, such a detonation would cause a 3,000 metre high column of water and debris and a five-metre tsunami while both the town and port of Sheerness would be overwhelmed.

The water wave would also reach the Isle of Grain and its liquid gas installations with potentially catastrophic consequences.

Meanwhile, London would also be flooded thanks to a ‘Thames tsunami’.

There are also lesser explosion scenarios.

The Royal Military College of Science estimated in 2004 that an explosion at low tide would be the most dangerous, having a damage radius of 2,500 km and would hit Sheerness.

Most recently media attention has focused on a recent survey, commissioned by the government’s Maritime and Coastguard Agency, which showed that the ship was degrading at a faster rate than expected.

However, it is understood that this decay has not increased the risk associated with the wreck.

That did not stop fears of the worst-case scenario being raised again.

So how likely is this ‘top event’ explosion?

KentOnline posed this question to Professor David Alexander from the University College London Institute for Risk and Disaster.

The 71-year-old has conducted 44 years of research in emergency planning and management and has been keeping a keen eye on the developments surrounding the shipwreck since 2017.

In 2019 the academic, who also works for Yamaguchi and Tohoku University in Japan, published a journal article on the case.

He said: “There’s a lot of literature surrounding the wreck which is rife with distortion, misestimation, speculation and exaggeration.

“This includes the idea of the ‘top event’ from the 1970 explosion tests which all reputable authorities agree is highly unlikely.”

However, the professor says the wreck is “not safe” because of the range of possibilities which could still cause a detonation.

He added: “An explosion could be caused by structural collapse, physical alteration of the bombs, collision by a ship or a deliberate detonation by terrorists.

“Whatever the cause of an explosion there is no doubt that serious risks remain.

“But there still isn’t the data for us to know whether all the bombs would explode if one was to detonate and what an explosion would look like.

"This is because we don’t know whether fuses are connected to some of the bombs due to the hastily pulled together cargo documents and because the water is not clear enough for photography inside the wreck to be very successful.

“In terms of what an explosion would look like we have a few different scenarios. There could be multiple explosions, for example, that were caused by a single explosion.

“So there’s a continued risk. The government’s line of thinking that the longer we leave the wreck the safer it gets is not backed up with a scientific consensus.”

So with the risk of explosion still present Professor Alexander believes that the bombs should also be removed from the site.

“They should have been removed a long time ago, the US has offered on two occasions to clear the wreck but both were declined,” he explained.

“Now it will be a very expensive undertaking and would take around six months to conduct the removal safely.

“There would also need to be the evacuation of around 40,000 people during the whole process. So there are no easy solutions.

“But it is better now than when the ship eventually falls apart completely which will make it hard to remove the bombs.”

While there are no plans to remove the bombs, the masts of ships, which protrude out of the water and have become a landmark for boat tours, are set to be removed this year by Department of Transport contractors.

This is to reduce the risk of the ship as it is thought the extra weight of the structures is placing an additional strain on the cargo hold – where the explosives are located.

But it poses another question about where these masts should go once cut down.

One veteran bomb watcher, Tim Bell, believes the masts should be turned into a landmark and planted in the Moat – a defensive canal dug to protect Sheerness from marauding invaders.

The Minster resident launched a campaign to stop the masts heading to Southend in June 2022 after rumours of the move hit the Island.

The 79-year-old has given talks about the ship to the Royal Engineers in Gillingham and has appeared on Channel Four News after immersing himself in the subject for more than 20 years.

His fascination with the wreck came after sailing near to the exclusion zone which sparked his research.

Mr Bell told KentOnline that he shares a similar view to Professor Alexander.

“The bombs should be removed,” he said, “especially if the masts are going to be cut down which provides a visual sign of where the wreck is for shipping.

“Its a matter of safety which has been neglected.

“The masts themselves are a tourist attraction as there are two tours you can take to see them.

”So it’s important that Sheppey gets to keep the masts and put them somewhere where they can continue to be an attraction.”

A Department of Transport spokesman said: “Our priority will always be to ensure the safety of the public and reduce any risk posed by the SS Richard Montgomery.

“We commissioned experts to carry out vital surveying work and we continue to monitor the site 24 hours a day and undertake detailed surveys to assess the wreck’s condition.”