When William Swallow testified that a ship hijacked by mutinying convicts had voyaged across the Pacific to Japan, where the crew encountered samurai, nobody believed him.

It's perhaps little wonder: Swallow told many lies in his lifetime.

One of the greatest was his name.

He had at least five aliases, changing them regularly to evade the authorities on his tail for various crimes — among them stealing a schooner of beer.

The man with blue eyes and a long nose was born William Walker, around 1790. Over the years he also went by the names Captain Waldon and William Brown.

But it's Swallow who became infamous — a pirate at the heart of one of Australia's greatest convict escape stories.

He left a trail of confusion that has taken almost two centuries of research to unravel.

And some mysteries remain — like whether Swallow also lied about his role in the mutiny.

Who was William Swallow?

Swallow was first brought from London to Van Diemen's Land — now Tasmania — in 1821, and given convict number 323.

Several years later, in 1829, he was part of a group of men who hijacked the brig Cyprus, an Australian supply ship.

He was eventually recaptured in China, and in 1830 was tried for piracy in a London court.

During the trial, Swallow gave a full account of the mutiny and the brig's voyage across the Pacific.

"I crossed the equator and ran North to latitude 38 degrees and made the coast of Japan being in want of wood and water and the ship being out of repair and having all her sails nearly split to pieces," he testified.

Swallow also gave details of the convict crew's week-long encounter with samurai in Japan.

But no-one believed his story.

His claims had long been discredited, until Japan-based historian Nick Russel translated part of a samurai manuscript in 2017.

Untangling history

Mr Russell compared details in the manuscripts with claims made by Swallow.

"What I'm doing is finding crucial things that just couldn't be there by fluke," he recalls.

"Like the cannonball — I don't know of any other incident where anything like that happened."

Historian Nick Russell helped to solve the mystery of an Australian pirate ship in Japan. ( ABC RN: Tim Stone )

Both Swallow's account and that of Hamaguchi Makita, the samurai chronicler, include eerily similar descriptions of a cannonball striking the hull of Cyprus.

"They opened fire on us and we received a shot between wind and water," Swallow testified.

The samurai account was similar: "Commander Mima ordered fire to be directed at the waterline where the ship was lined with copper. Two cannonballs hit and shook the ship badly."

Comparing the two accounts helped Mr Russell verify the ship in the Hamaguchi manuscripts as the Cyprus.

In doing so, he found the missing piece in one of Australia's greatest convict escape stories: the Cyprus' journey from Van Diemen's Land, through the Pacific to Canton.

A painting of the ship by Makita Hamaguchi. ( Supplied: Tokushima Prefectural Archives )

"[Japanese] historians have said they thought the ship sailed out and sank, so they didn't pursue it," Mr Russell says.

Mr Russell says a letter was "another key point".

During an encounter with Japanese samurai, Swallow presented them with a letter to take back to their commanding officer.

It was conveyed to shore where the samurai were promptly reprimanded.

The samurai commander's response, recorded by Hamaguchi, was: "Don't accept anything from the barbarians, take the letter back immediately."

It's not always clear-cut

Of the convicts involved in the mutiny, Swallow is the only one to mention the encounter in Japan, and this has troubled researchers for many years.

But for Warwick Hirst, who has authored a book on Swallow, that is what motivated him to put pen to paper.

"There's no other account of the voyage I could find," he says.

He cautions that because it can be difficult for historians to find primary source material, "you have to be willing to admit that you never really know what happened, especially if you only have one person's account".

But he has always believed there was "a very strong possibility that [Swallow] did go to Japan".

"And now Nick Russell has found the evidence," he adds.

A depiction of Hobart in 1825 by Augustus Earle. ( Supplied: State Library NSW )

Hamish Maxwell-Stewart, a professor of history at the University of Tasmania, suggests that history is not always so clear-cut.

"In the past historians have been reluctant to believe the testimony of prisoners," he says.

"Although Swallow was not believed, when you actually place the testimony of prisoners under scrutiny it turns out to be pretty accurate.

"Prisoners lied but when they did it was highly strategic."

Both men are convinced that one such strategic lie was told during Swallow's trial.

Swallow had found himself conveyed aboard the Cyprus following an escape attempt from Hobart-Town Barracks.

During the voyage Swallow fell ill with stricture, a urinary blockage, and was operated on by Walter Williams, the 20-year-old surgeon aboard the Cyprus.

It was while he was recuperating below deck that Swallow claims the mutiny took place.

The claim was later substantiated by Williams during the trial in London.

The surgeon's evidence in support of Swallow changed the course of the convict's life.

In the eyes of the jury, Swallow went from alleged leader of the mutiny to unwilling participant.

"I'm certain he was the ringleader," Hirst insists.

"Swallow was a very clever man."

Maxwell-Stewart agrees.

"As the only skilled sailor aboard the Cyprus when she was taken, Swallow successfully claims he was forced to take part in the mutiny," he explains.

"This is of course a lie."

Found not guilty for the piracy of the Cyprus, Swallow was transported to Tasmania to serve out the remainder of his sentence.

He was sent to Macquarie Harbour, and later transferred to Port Arthur, where he died on May 12, 1834.

He is buried in an unmarked grave on the Isle of the Dead.