In 1943, a camouflaged ship set off from Australia to England carrying top secret cargo - a single young platypus.

Named after his would-be owner, UK prime minister Winston Churchill, the rare monotreme was an unprecedented gift from a country desperately trying to curry favour as World War Two expanded into the Pacific and arrived on its doorstep.

But days out from Winston's arrival, as war raged in the seas around him, the puggle was found dead in the water of his specially made "platypusary".

Fearing a potential diplomatic incident, Winston's death – along with his very existence – was swept under the rug.

He was preserved, stuffed and quietly shelved inside his name-sake's office, with rumours that he died of Nazi-submarine-induced shell-shock gently whispered into the ether.

The mystery of who, or what, really killed him has eluded the world since - until now.

Two Winstons and a war
The world has always been fascinated by the platypus. An egg-laying mammal with the face and feet of a duck, an otter-shaped body and a beaver-inspired tail, many thought the creature was an elaborate hoax; a taxidermy trick.

For Churchill, an avid collector of rare and exotic animals, the platypus's intrigue only made him more desperate to have one – or six – for his menagerie.

And in 1943 he said as much to the Australian foreign minister, H.V. 'Doc' Evatt.

In the eyes of Evatt, the fact that his country had banned the export of the creatures - or that they were notoriously difficult to transport and none had ever survived a journey that long - were merely challenges to overcome.

Australia had increasingly felt abandoned by the motherland as the Japanese drew closer and closer – and if a posse of platypuses would help Churchill respond more favourably to Canberra's requests for support, then so be it.

Conservationist David Fleay – who was asked to help with the mission – was less amenable.

"Imagine any man carrying the responsibilities Churchill did, with humanity on the rack in Europe and Asia, finding time to even think about, let alone want, half-a-dozen duckbilled platypuses," he wrote in his 1980 book Paradoxical Platypus...