The wreck of an historic Royal Navy submarine has been plundered by thieves who dived 90ft to the sea bed to remove part of it.
HMS Holland, which sank in bad weather off the Sussex coast while being towed to a scrapyard in 1912, is protected by law because of its historical importance.
Now police are investigating after divers from the Nautical Archaeology Society discovered during a routine check that its torpedo tube hatch is missing.
Thieves are thought to have floated the 66lb piece of ironwork to the surface in 90ft of water by attaching buoyancy balloons.
Experts say it was an audacious raid which may have been carried out at the request of a collector with an interest in naval history. Both Sussex Police and English Heritage, which is responsible for the wreck's care, have appealed for the return of the artefact and hope that someone in the diving community may provide them with a lead.
Police say that whoever took the hatch, which is about 30in in diameter, is liable for prosecution under the Protection of Wrecks Act.
The Holland 5, as the wreck is known, lay undiscovered until the mid-Nineties. It is the only surviving example of five Holland class vessels commissioned by the Admiralty to test the fighting capability of submarines, which were at the time a relatively new type of technology.
They were top secret and only a few senior officers and crew knew of their existence.