Image copyright Getty Images/UK Government Art Collection Image caption Was Tomas Masaryk (L) the illegitimate son of Emperor Franz Joseph?

A Czech DNA expert is carrying out tests on clothes belonging to the first president of Czechoslovakia, Tomas Garrigue Masaryk.

The tests should provide a definitive answer to an explosive claim that has fascinated readers and troubled historians for almost a century. Was Masaryk - champion of Slav rights and father of the Czechoslovak state - the illegitimate son of the Austro-Hungarian emperor?

"So," said Marek Vareka, a historian at the Masaryk Museum in Hodonin. "Here we are."

The car came to a halt at Holic Castle, on the Czech border with Slovakia. In front of us stood a forbidding, three-storey baroque pile encircled by a grass moat.

Image caption Holic Castle is on the Slovak side of the border and in 1849 hosted Emperor Franz Joseph

"Back then the Habsburgs owned both the estates of Hodonin and Holic, so they stayed here often," Mr Vareka explained.

Today, the towns are separated by an international border. Hodonin is Czech, Holic is Slovak.

In 1849, the border was internal: Hodonin was in the imperial crown land of Moravia, Holic in the Kingdom of Hungary. But it was all "the Empire" to the Habsburgs.

"We do know Emperor Franz Joseph came through Hodonin and Holic in December 1849, on his way to inspect the imperial troops who'd put down the Hungarian rebellion in the summer," Mr Vareka told me.

Image caption Marek Vareka says there is no record of the emperor meeting the local cook

I closed my eyes and tried to imagine, not Franz Joseph the mutton-chopped kaiser of World War One, but Franz Joseph the 19-year-old sovereign, resplendent in red and white military uniform, sitting ramrod straight on his imperial horse as it trotted into the castle grounds.

He was here in December. Could he have been here in the summer, too?

And could he have been provided with female company, to while away the hours?

"Oh, that would have been quite normal," says Mr Vareka, explaining that the imperial staff selected clean, healthy local women for the emperor.

And could, perhaps, that woman have been Theresia Kropaczek, a cook at the Habsburgs' Hodonin estate?

Image copyright Getty Images/Schloss Schoenbrunn Image caption DNA tests will decide whether Masaryk (L) was the emperor's son

The same Theresia Kropaczek who married her co-worker Josef Masaryk in August 1849, yet gave birth to Tomas just seven months afterwards?

Could Tomas Masaryk have been the emperor's illegitimate son?

Frankly the evidence is entirely circumstantial. Mr Vareka stresses there is no record of Theresia Kropaczek or Franz Josef even meeting, let alone sharing a bed. It's all pure hypothesis.

But that has done little to dampen speculation.

For a start, German-speaking Theresia was 10 years older than her husband, an illiterate Slovak coachman. She was also from a higher social class.

Throughout his early life, Tomas - a boy from humble origins in Moravia - appeared to have a protective hand hovering over him.

"Lots of things don't quite add up," said Czech TV documentary maker David Vondracek.

"Even as a child he moved in aristocratic circles. He was a tutor to the wealthiest Austrian families," he went on.

Who was Tomas G Masaryk? 1850 Born, son of a Slovak coachman and a cook

1882 Became professor of philosophy in Vienna

1900 Founded Czech Progressive party

1918-35 President of Czechoslovakia

Mr Vondracek finds it extraordinary that Masaryk was expelled from an academy in Brno because of a disagreement with the headmaster but then admitted to the most prestigious gymnasium in Vienna.

"And one of his greatest benefactors was the Viennese Chief of Police Anton von Le Monnier, who was a close confidant of Franz Joseph," he added, explaining his own personal fascination with the theory.

Now he wants to solve the mystery using DNA.

He has obtained a suitcase of clothes that once belonged to Tomas Masaryk.

Genetic material on them is being compared with that of his late son Jan, to establish whether they are truly his.

Image copyright AFP Image caption Masaryk's DNA may be compared with the Habsburgs, including Archduke Franz Ferdinand

If they are, that DNA will be compared with that of living male descendants of Josef Masaryk, the man believed to have been his father.

If there is no match, it will then be compared with Habsburg DNA - either from living Habsburgs or from artefacts in Czech museums, such as a bloodstained handkerchief belonging to Archduke Franz Ferdinand, whose assassination in Sarajevo sparked off World War One.

And if a match is found, it will be time to start rewriting the history books.

Czech TV will announce the results in a few months' time. For some, it cannot come soon enough.

I'd like this debate to be settled once and for all. That's why I agreed for his clothes to be examined" Irena Chovancikova, Masaryk Museum

"Personally, as a historian, I wouldn't have bothered looking into it," said Irena Chovancikova, director of the Masaryk Museum, clearly bristling at the revered president being subjected to such indignity.

"Masaryk always talked about Joseph as his father. The father-son relationship was clear for all to see," she told me, as we sat in the splendour of Prague's Municipal House, where Czechoslovak independence was declared in October 1918.

"It all seems a very tabloid way of approaching things; at times the debate has been simply disgusting."

Disgusting? Maybe. But it could turn the history of Central Europe on its head.