Masts removed from bomb-laden WWII ship in Thames in bid to avoid explosion

A sunken US wartime ship in the Thames estuary holding enough unexploded bombs to devastate a Kent coastal town and send a tidal wave through London has been made slightly safer, ministers have announced.

Engineers have removed the masts of the SS Richard Montgomery – a second world war cargo ship that sank in 1944 with approximately 1,400 tonnes of munitions onboard – without triggering the kind of feared explosion that has kept the wreck under constant guard for decades.

The work was carried out because of concerns that the masts, which had remained visible above the water near Sheerness, could collapse in on the deadly cargo and blow up the ship.

The potential effects of an explosion after 82 years under water have divided expert opinion. Some believe it could cause a small tsunami, throw debris 3km into the air, and “level Sheerness”, according to a New Scientist report in 2004. A government report in 2000 said it was widely accepted it would “put property and the local population at risk”.

The exact contents of the ship’s three holds are unknown but a defence agency report estimated there were almost 300 2,000lb (900kg) blockbuster bombs and more than 2,000 cluster bombs.

Keir Mather, the maritime minister, told the Commons on Monday that work had now been completed, with all three masts successfully removed in “complex project requiring specialist programme, engineering and risk management expertise”.

Mather said that the masts had put “significant load on the structure and their removal has reduced that risk and supports the long-term safe management of the site.”

He said work was completed ahead of schedule and below forecast costs, an estimated £9.5m. The masts have now been delivered to a maritime museum, the Historic Dockyard Chatham, “in recognition of the historic significance of the SS Richard Montgomery and its role in supporting the allied forces’ efforts during world war two”.

The wreck would “continue to be subject to continuous monitoring and control via the established exclusion zone”, he said.

A shipping exclusion zone has long been in place around the SS Montgomery, and since 2025 a no-fly zone has been in place – a development that could have been awkward had Boris Johnson’s proposed Thames estuary airport gone ahead.

Although the risk of an accidental major explosion is now deemed remote, local people have been alarmed by incidents in recent years, including the occasional close proximity of cargo shipping, and a paddleboarder who uploaded pictures to social media of himself leaning on the protruding masts.