The remains of explorer Matthew Flinders have been found at a burial site beneath Euston station in London, 216 years after he circumnavigated Australia.

Key points: Matthew Flinders died at the age of 40

Matthew Flinders died at the age of 40 The explorer's remains were discovered thanks to a well-preserved lead breast plate

The explorer's remains were discovered thanks to a well-preserved lead breast plate His headstone was removed in the 1840s and it was feared his remains had been lost

His remains were identified by archaeologists working on the controversial HS2 high-speed rail project, thanks to a well-preserved lead breastplate.

"I was rather hoping that there would be a ship or an anchor — something that linked him to his nautical endeavours," Helen Wass, the project's heritage chief, said.

"But it's just so exciting to see that here and to know that this was his grave."

Workers remove the breast plate from Matthew Flinders burial site. ( Supplied: HS2 Limited )

Flinders circumnavigated Australia between 1801 and 1803.

Among his crew on HMS Investigator was Indigenous sailor Bungaree, credited with being the first Australian to sail around the continent.

Flinders died at the age of 40, the day after the book detailing his journey, A Voyage to Terra Australis, was published.

He was interred in what was then St James's burial ground on July 23, 1814.

For years, experts thought the explorer was buried under what became platform 15 at Euston station. But while Flinders's remains were found at Euston, they were not under platform 15.

"The records show that he was buried here. He died in a house not very far away from this site," Ms Wass said.

"An urban myth was that he was buried under platform 15 of the modern Euston station — we now know that is not true."

The cemetery at St James soon became overcrowded. Originally designed for 16,000 bodies, it quickly expanded to about 60,000.

Euston station expanded into the burial ground in the 1840s. Flinders's headstone was removed, and it was feared his remains had been lost forever.

Now, it's the site of one of the largest infrastructure projects in British history — the $101 billion HS2 rail link between London and Birmingham.

The unearthing of Flinders's lead breastplate helped confirm the discovery. ( Supplied: HS2 Limited )

As part of the painstaking project, a team of archaeologists and specialists are exhuming about 40,000 graves.

Many will never be identified, but the unearthing of the lead breastplate attached to Flinders's coffin confirmed the discovery of the British navigator.

An archaeologist leans over Matthew Flinders's grave. ( Supplied: HS2 Limited )

"The archaeologists go through a very rigorous process, so once they identify a grave area you can tell by the different coloured soil," Ms Wass said.

"You get a grave-shaped patch of ground and then they carefully use their hands and their tools to scrape away the soil.

"Obviously as soon as you start to see any type of coffin plate you know that that might have biographical information about the person who's buried there.

"Of course, he's at the slightly more affluent end of the burial ground.

Archaeologists and specialists are exhuming about 40,000 graves. ( ABC News: Tim Stevens )

"St James Chapel is just beyond his grave, and generally the richer you were … the closer you were buried to church, to God".

The burial site includes the remains of other notable figures, including the founder of Christie's auction house and American boxer Bill Richmond, but Flinders is its most renowned resident.

Archaeologists hope to find a name plate on Captain Flinders's coffin. ( Supplied: MOLA Headland Infrastructure )

"This is a very exciting moment for Australia," Australian High Commissioner to the UK George Brandis said outside the station, standing beside a statute of Captain Flinders.

"It is serendipitous the discovery of the remains of Matthew Flinders, one of the great early explorers, should come in the week of Australia Day".

Flinders's remains will undergo testing for more clues about his extraordinary life before he is interred with the other bodies at an undecided site.

Archaeologists frequently discover remains underneath London during digging works for rail links.

Flinders University honorary senior researcher Gillian Dooley, said Flinders — the university's namesake — could now "be treated with the respect he deserves".

"Even in death, after his short and unsettled life, he hasn't been allowed to rest in peace in the English countryside, which is what he wished for. Let's hope this can now be achieved," Dr Dooley said.

In 2013, 20 Roman skulls were uncovered in a dig for the city's Crossrail project.

Archaeologists said it was possible the remains, found along the River Thames, dated back to a rebellion by the British queen Boudicca.

In 2015, experts uncovered a mass grave of thousands of plague victims underneath Liverpool Street station.