Britain's 'real monarch' gets King Charles coronation invite. Know the story

As the son of a farmhand from the Australian outback, Simon Abney-Hastings might be an unlikely choice to receive an invitation to King Charles III's coronation.

But when he takes his seat in Westminster Abbey next week, he will be the one person other than those in the line of succession who could actually have a claim on the throne.

Unlikely though it might seem, the scenario is based on research by British medieval historian Michael Jones.

Two decades ago he uncovered a document in Rouen cathedral in France which he says is proof King Edward IV was illegitimate.

During the five weeks when Edward might have been conceived, according to Jones, his fahter Richard of York was in fact 160 kilometres (100 miles) from his wife Cecily Neville, the Duchess of York.

As a result, Jones has argued, Edward was not the rightful heir to the throne and the line of succession should instead have gone through Edward's younger brother George, Duke of Clarence, who is a direct ancestor of Abney-Hastings.

Golden spurs

Although the family does not possess any lands or stately homes in the UK, by virtue of their lineage they inherited the ancient Scottish title of Earl of Loudoun.

Abney-Hastings' father Michael emigrated from the UK to Australia in 1960.

Michael inherited the title from his mother, the 13th Countess of Loudoun, in 2002 and it passed on his death in 2012 to Simon, who is the 15th earl.

In recognition of the family's heritage, Simon Abney-Hastings, 48, is one of just 13 individuals carrying out ceremonial roles largely because they successfully proved that their forebears played a particular role at previous coronations.

The current earl said on Twitter he was "delighted and sincerely honoured" to be asked to perform the same role as his ancestors on May 6.

The earls of Loudon have traditionally been the bearers of the golden spurs as far back as the 12th century.

In earlier centuries the spurs -- signifying the monarch's role as head of the armed forces -- were attached to the new sovereign's feet.

In more recent times they have just ceremonially touched the heels of the monarch before being placed on the altar.

'King Michael I'

The surprising implications of the Rouen cathedral discovery came as a shock to the Abney-Hastings family nearly 20 years ago.

A British documentary team visited an unsuspecting Michael Abney-Hastings at his home in Australia for the 2004 programme "Britain's Real Monarch".

To the amusement of his family, they were told that new research pointed to Edward IV being illegitimate, which "means that you are the rightful king of England".

Abney-Hastings responded that he had been aware of a "distant" link to the Plantagenet royal dynasty but confessed that the news that he might have been King Michael I was "a bit of a shock".

An Australian, Simon lives in Wangaratta in the southeastern state of Victoria, and appears to have no plans to press any claim.

His lawyer and private secretary Terence Guthridge told AFP that although historians might believe he has the right to inherit the throne, the 15th earl "has never held this view".

In fact, he had always been a "loyal and staunch supporter" of both Queen Elizabeth II and her son, he said.

"Indeed they exchange birthday or Christmas cards every year," he added.