Tony Rennell - The madcap Englishman was in a sanatorium, spaced out on amphetamines as he combated crippling chronic exhaustion from over-work. But as he slid between the extremes of fatigue and a blissed-out chemical high, his mind, as always, was racing at the speed of light, struggling with the complexities of his latest brainwave.

Aircraft carriers made from ice! From his days as a Cambridge undergraduate, ideas had always tumbled out of Geoffrey Pyke’s head - off-the-wall ones, so far outside the box that only a genius, or madman, like him would dare to go there.

In looks and mannerisms he was odd, resembling his cousin, Magnus Pyke, who a generation later would become the epitome of the bonkers television boffin.

For sheer brain power, though, he was almost unique. A fellow scientist likened him to Einstein, the sort of free-thinker who could have invented the wheel.

Now, at the height of World War II, the 49-year-old’s job was to think the unthinkable in search of unconventional ways to beat Hitler. Throw away the rulebook was his only guiding rule. Be outrageous, iconoclastic, fearlessly inventive.

Thus, when considering how to hide a vehicle sent behind enemy lines during an undercover operation, he suggested putting it inside a tent with a sign in German saying: ‘Officers’ Latrine. For Colonels only’ - in the certain knowledge, he felt, that no rule-bound German soldier who stumbled on it would dare look inside.

A childish joke or inspired? With Pyke - whose mind-boggling story is told in a new book - no one could ever be sure. Another suggestion, made in all seriousness, was to drop Hitler lookalikes on to occupied Greek islands to order the German garrisons there to surrender.

The ‘colonels’ latrine’ brainwave was canned, like 99 per cent of the output from his over-active brain -‘Pyke’s Nonsense’, as it was known. The Hitler clones idea, one suspects, never got further than the pub. But the next one - there was always a next one - soon had an army of devotees.

It was 1941 and German submarines had the upper hand in the Battle of the Atlantic, sinking too many ships bringing vital supplies to Britain from the United States. A whole fleet of new aircraft carriers was urgently needed to protect convoys in the Atlantic shipping lanes.

Pyke came across an obscure article in an old dog-eared copy of the National Geographic Magazine about the immense strength of icebergs and their ability to absorb shell fire without cracking apart.

His eccentric mind saw the potential. Why not convert icebergs into mid-Atlantic floating air bases with a runway on the top? It was one of the strangest and most ambitious ideas of the war - from a man whose own wife had once considered him borderline insane.

He threw himself into research, soon discovering that if water was mixed with wood pulp and then frozen, the ice became super-strong and also took much longer to melt. Here, he reasoned, was a formidable new material from which to construct huge, unsinkable ‘berg-ships’ to act as floating airfields.

From his hospital bed, he sent his idea to Lord Louis Mountbatten, a cousin of the King, whom Winston Churchill had installed as the head of Combined Operations to come up with dotty ideas that might just win the war.

Mountbatten was so impressed by Pyke’s zany thinking that he appointed him his director of programmes. Pyke argued that, from this reinforced ice, ‘gargantuan’ ships twice the length and width of the ocean liner Queen Mary could be constructed. They would be ‘the largest vessels ever made by man and unsinkable’.

Shells designed to sink conventional metal ships would have little or no impact - and if they did make holes these could be quickly repaired with extra ice. Magnetic mines would drift harmlessly past; torpedoes would perforate the ship without sinking it.

He envisaged hundreds of unstoppable and impregnable ‘berg-ships’, guided by propellers, lumbering around the world and into enemy ports, where they could merrily ‘smash up every ship there’.

He named his proposal Habakkuk, after the Old Testament prophet who warned: ‘Be utterly amazed, for I am going to do something in your days that you would not believe, even if you were told.’

Mountbatten, every bit as mercurial as Pyke and, like Churchill, with a weakness for inventors with ‘corkscrew minds’, was duly amazed. Within three hours of reading Pyke’s paper, he set the wheels in motion. His staff pored over the proposal and pronounced it ‘both sound and brilliant’.

Churchill, entranced by the idea of a floating airfield made of ice, came enthusiastically on board too. ‘Berg-ships’ could solve his Atlantic supply problems.

They could also be the key to invading Norway and kicking out the Nazis, one of Churchill’s obsessions. The project was gathering momentum.

Meanwhile, in a secret refrigerated laboratory five floors below London’s Smithfield Meat Market, the best mix of water and wood pulp was worked on to produce ice that was as strong as concrete.

The end product - which even a rifle bullet could not shatter - was given the name of ‘Pykrete’, to honour its inventor. Mountbatten, ever the drama queen, took a sample to Chequers, the prime minister’s country house, and popped it into a startled Churchill’s hot bath.

The super-ice cube did not melt but continued to float. Eyes popped in amazement. Both men were now convinced that this reinforced ice might well be ‘the most important single idea of this war’. Huge resources were ploughed in, and, on a frozen lake in Canada, work began round-the-clock to build a scale-model 60ft long and 1,000 tons in weight.

One exciting discovery during this process was that blocks of Pykrete were essentially self-adhesive and had only to be placed next to each other at suitably cold temperatures for them to start bonding.

This would dramatically shorten the process if and when these ships went into full-scale production.

In London, though, pressure for even quicker results was growing. The Battle of the Atlantic was now going so badly that some in the Admiralty proposed abandoning convoys altogether.

Churchill wrote reassuringly to his chiefs of staff with news of his ‘berg-ships’ and his hope that the first three would be ready in little over a year. He had reason to be optimistic. On that frozen lake in Canada, the finished model was successfully cut away from the ice on which it had been built and showed no signs of melting.

For propulsion, 26 propellers would be spaced along each side. A rudder and a wooden stern and bow would be fitted. All systems were go. And then a major problem surfaced. Pykrete was robust enough to withstand bullets and shells but it had a dangerous tendency to sag under its own weight - and a warship that collapsed once it put out to sea would be no good to anyone. Pyke had no doubt he could find a solution - in his mind, every question had an answer, eventually - but, at the War Office, the tide was turning against the whole Habbakuk concept.

The establishment figures there had never felt comfortable with the slovenly Pyke, his strange manners and bolshie personality. One fellow scientist was positively hostile towards him, dismissing him as a fraud who, as he put it, ‘clothes commonplace ideas with garrulous pseudo-scientific blather’ and dealt in ‘pretentious nonsense’.

A secret report damned Pyke’s project as unproven, too costly and too slow. It also emerged that the giant refrigerators needed to make Pykrete would consume as much steel as building metal warships.

Though Pyke argued his case strongly, damage had been done. It didn’t help his cause that other improvements in weaponry and tactics were helping turn the corner in the Battle of the Atlantic.–Daily Mail