Divers seeking the Tsar’s priceless Amber Room from the torpedoed Nazi cruise liner Wilhelm Gustloff have been threatened with jail for ‘grave-robbing.’

Polish charts only mark the wreck, on which up to 7,000 Germans fleeing the Soviet Army in World War II, as ‘obstacle 73’ in a bid to keep her whereabouts in the Baltic Sea secret.

But now that items such as ashtrays are selling for 6,800 (pounds sterling) each the wreck’s allure is becoming too great to resist.