In a refrigerated room hidden beneath London’s Smithfield Meat Market in 1943, behind a screen of hanging animal carcasses, a future Nobel Prize winner was busy perfecting a recipe. Not for food — for a building material. His task: prove that you could build the largest warship in history out of frozen water.

This was Project Habakkuk, and it is perhaps the most gloriously mad idea the Second World War ever produced. It also came astonishingly close to happening.

The Hole in the Ocean

The problem was deadly serious. In the middle of the Atlantic lay an “air gap” that no land-based aircraft could reach, and it was there that German U-boat wolfpacks tore into Allied convoys with near impunity. Steel was scarce and real aircraft carriers scarcer. The eccentric British inventor Geoffrey Pyke proposed an outrageous fix: a vast, unsinkable floating island made of ice, parked in the gap as a runway for anti-submarine aircraft.

Bulletproof Ice

Plain ice was useless — brittle, and it melts. The breakthrough was a material called pykrete: ordinary water mixed with about 14% wood pulp and frozen solid. The wood fibres act like the steel rebar in concrete, and the result is startling. Pykrete is far stronger than ice, melts much more slowly, and is so tough that a rifle bullet barely dents it. Molecular biologist Max Perutz — later a Nobel laureate — perfected the formula in that secret meat-market cold room.

The story goes that to convince the brass, Lord Mountbatten produced a block of pykrete and demonstrated its strength — in one telling, by firing a pistol at it in front of startled Allied commanders, the bullet ricocheting wildly off the ice.

A Ship the Size of a Small Town

The numbers were staggering. The full Habakkuk would have stretched some 2,000 feet, displaced around two million tons, carried up to 200 aircraft, and needed a crew of thousands — all kept frozen solid by an internal network of refrigeration pipes. Pyke named his ice leviathan after the Biblical prophet Habakkuk, who promised something so wondrous “you would not believe it even if you were told.”

The Lake in the Rockies

To prove it could work, a team built a 60-foot scale model on Patricia Lake in Jasper, Alberta, complete with embedded cooling pipes. It performed well — so well that even after the project ended, the little iceberg took three hot Canadian summers to fully melt. But by then the war had moved on. New very-long-range aircraft and small escort carriers finally closed the mid-Atlantic gap, and the need for a floating ice continent simply evaporated.

Habakkuk was quietly shelved. The remains of the prototype still rest on the bed of Patricia Lake to this day — the sunken proof that Britain very nearly went to war on a ship made of ice.

Sources: 99% Invisible; Warfare History Network; War History Online; Alberta Aviation Museum; Wikipedia.