War was the talk of Europe's foreign ministries and workmen were digging air raid shelters in London's parks, but the great politician Winston Churchill had other things on his mind.

As his fellow MPs debated the threat from planes and bombs, the future prime minister was absorbed in a different form of flight: a grand plan for a butterfly garden at his country home Chartwell, in Kent.

Ebullient as ever – he was also bricklaying his own wall and digging a pond – Churchill proposed action on an heroic scale which a new project, launched today by the National Trust, commemorates. He envisaged "fountains of honey and water" and attempted to reintroduce an extinct species, the black-veined white, by breeding imported caterpillars in muslin bags tied to his hawthorn hedge.

"It was a wonderful example of the power the natural world can have on all of us, even great war leaders," said Matthew Oates, nature conservation adviser at the trust, who has supervised the recreation of Churchill's breeding house in Chartwell's disused game larder. "His enthusiasm may have got the better of him, because the reintroductions ended in farce, but we can genuinely honour him as a pioneering butterfly gardener."

The trust's initiative has just seen the first release of captive-bred butterflies – six peacocks and a brood of painted ladies – since the early 1950s, when Churchill sat in retirement, painting and watching the insects hatch. The trust has restored the summer house which Churchill converted from the larder, including the muslin curtain over the door, which kept butterflies in until the weather was right for a release.

"Churchill was famous for his garden parties at Chartwell, and we think that the butterflies had a part in that too," said Oates. Romantically, the war leader thought that his hatches would flit joyfully about the Victorian mansion's gardens, but most dispersed into Kent.

"We know nowadays that this is what happened, but Churchill and his adviser, the BBC's radio 'butterfly man' Hugh Newman, got a little carried away," said Oates. The pair egged one another on in the reintroduction project, which also involved a European sub-species of the very rare British swallowtail.

"Churchill phoned Newman out of the blue in the summer of 1939, probably after hearing him on the radio and learning about his 'butterfly farm' at Westerham, just a couple of miles from Chartwell," said Oates. The war intervened before the great man's plans could really get going, but in 1946 Churchill wrote to Newman again, saying: "Let me have your plan soon, and let it be a plan of action."

The Trust's programme of releases will be confined to familiar British butterflies, from the 20-odd species found at Chartwell, because foreign introductions are now banned or extremely strictly supervised by international codes of practice. Churchill's plans were made in ignorance of habitat and climate changes which had doomed the Black-veined White, but also suffered humdrum disasters.

"His gardeners mistakenly cut down and burned the fennel where his swallowtail caterpillars were breeding," said Oates, "and the fate of the black-veined whites was even worse. Newman sent a message when the time had come for the caterpillars to pupate, saying 'remove the bags'. He meant 'open them' but the gardeners misunderstood that too, pulled the bags off, caterpillars and all, and burned them too."

The debacle appears to have dispirited even Churchill, whose interest in butterflies began at the age of six, when he wrote to his mother, Lady Jennie Churchill: "I am never at a loss to do anything while I am in the country for I shall be occupied with 'butterflying' all day (as I was last year)." He also collected on military campaigns in the Sudan, Pakistan and South Africa, but from the mid-fifties, the Chartwell project fell into disuse.

"It is marvelous that butterflies are thriving at Chartwell again," said Dr Martin Warren, chief executive of the British charity Butterfly Conservation. "Churchill's planning of this butterfly house, and his pioneering butterfly garden, inspired many others and helped spread his enthusiasm."

Other work at Chartwell has revived plants including a huge buddleia, or "butterfly bush", which date from Churchill's planning with Newman. But the honey and water fountains, which defied even the former premier's ingenuity, remain unrealised, except on educational panels at the mansion.

Famous fanciers

Churchill's predecessor Neville Chamberlain collected butterflies in Britain and the Caribbean before concentrating on his first love, birds. On the eve of war in 1939, his diary noted sparrowhawks flying over the Foreign Office.

The air vice marshall Sir Robert Saundby, second-in-command to Sir Arthur "Bomber" Harris, was a collector. A butterflying friend sent him useful aerial photos of Hitler's mountain retreat at Berchtesgaden after finding them in a pre-war German collector's album.

The physician Sir Cyril Clarke solved the genetic "blue baby" blood condition in infants during the 1950s through studies of the swallowtail butterfly which he bred next to his consulting rooms.

Vladimir Nabokov, the author of many books including Lolita, was an expert on butterflies. He discovered several new types, and the genus, or butterfly family, of Nabokovia is named after him.

Joseph Grimaldi, London's most popular clown in Victorian times, walked to Kent on days off to catch the rare adonis blue. When his butterfly collection was stolen, he turned to pigeon fancying instead.