Wartime plans to construct an aircraft carrier out of ice left one Navy News reader bemused - but the tale is true.

Mr M Stanford wrote to us from Ramsgate saying that a friend of his had just had a holiday in Canada, where he visited Lake Patricia.

There he saw a plaque which described trials carried out during World War II intending to create an aircraft carrier out of two million tons of ice.

Mr Stanford and his mates, pilot launch crews, had a good laugh at the idea - but it was true.

Operation Habbakuk was the name of the plan by eccentric British boffin Geoffrey Pyke to construct, from a form of ice, either a 'relay floating air base' for long-range aircraft, an aircraft carrier for shorter-range anti-submarine patrols, an advance fighter base, or a cargo carrier.

A copy of the directive, as agreed by the Deputy First Sea Lord and dated April 9, 1943, is kept at the Fleet Air Arm Museum at Yeovilton in Somerset.

The directive states: "The ultimate function of the vessel is not specified at this stage, apart from the fact that it must be unsinkable …"

According to Pyke's cousin Magnus, the celebrity TV scientist, Geoffrey Pyke realised that with the addition of between four and fourteen per cent wood pulp as water freezes, a very hard, durable and buoyant substance is produced, which was named pycrete or pykrete in his honour.

Churchill was interested in the prospects for huge vessels made of pycrete, but Allied advances in the war - including the Normandy landings - and the relative cheapness of steel aircraft carriers, led to the scheme being abandoned.

So artificial 'berg-ships', up to 2,000ft long with 30ft thick hulls, containing hangars, accommodation, a refrigeration plant and banks of diesels to power them at less than seven knots, never saw the light of day, despite the fact that torpedoes would have caused barely a dent and they were impervious to bombs.

It was estimated that a torpedo would cause a crater a metre deep and six metres across, which could quickly be repaired using sea water, wood pulp and the cold air which would circulate throughout the berg-ship in cardboard tubes.

The prototype berg-ship - a framework of wood and pycrete blocks - floated throughout the summer on Lake Patricia, sinking later that year. Divers later found the remnants on the lake bed, and a plaque was recently unveiled to record the experiment.

Navy News would still like to hear from anyone who has further details of Operation Habbakuk, or any other far-fetched ideas which never made it past the theoretical stage.