Prince Ernst August of Hanover has rarity value in Germany: a blueblooded aristocrat with a jetset lifestyle, he is married to Princess Caroline of Monaco, is a cousin to Queen Elizabeth and he brings a touch of glamour to a country short on celebrities.

But how gentle is that touch? Could it be that the man who styles himself His Royal Highness, the Prince of Hanover, Duke of Brunswick and Lüneburg, Prince of Great Britain and Ireland, is capable of using a knuckleduster to beat up someone who crosses his path?

That was the question concerning the regional court in Hildesheim, north Germany, yesterday.

Prince Ernst August, 54, was found guilty in 2004 of causing grievous bodily harm in Kenya to a disco owner whose loud music and laser show had disturbed his evening peace. Now, claiming that he had been misrepresented in the original court hearings, he is demanding a retrial.

“It is important for him to establish that he is not the kind of person who would set about somebody with a knuckleduster and cause injuries,” said Hans Wolfgang Euler, his lawyer.

“My client has never owned a knuckleduster in his life or held one in his hand.”

The Affair of the Royal Knuckleduster began eight years ago. The Prince was trying to enjoy the balmy night air with Princess Caroline on the Kenyan island of Lamu.

About 800 metres away on the beach of Manda island, Josef Brunlehner, a German discotheque owner, 59, was watching his customers rave to techno music.

He received a call saying that the Kenyan authorities were measuring his noise levels and that he should cross to the other side of the water. When he got out of the boat, Prince Ernst August hit him. That much is undisputed. The Prince says he merely cuffed the fellow German round the ears, saying: “This one's for the music, and this one is for the light.”

Mr Brunlehner says that he was beaten so seriously by the Prince that he had to be flown to the emergency unit of Mombasa hospital.

Photographs were taken of the injuries and a senior forensic scientist, Hans-Dieter Troeger, of the medical faculty of Hanover University, has testified that the wounds must have been inflicted by a “half-sharp instrument”.

That was enough for the first judges to fine the Prince 445,000 euros (£355,000), giving him a criminal record. The court was told that the enraged Prince, while punching his victim, had yelled out: “You German pig. You pimp. I'll put a mafia gang on you and they will slice you up.”

Now the Prince has found five Kenyans who were on the beach at the time and are ready to say that he did not use any kind of weapon. They have been flown to Germany.

The knuckleduster is central to the case. If the Prince used only his bare fists he could hope, in a retrial, to face lesser charges of assault or even slander. If he can persuade a court that he simply lost his temper, he may yet extinguish his criminal record.

Unfortunately his first lawyer, Jochen Heidemeier, conceded in the 2004 trial that the Prince had drunk substantial amounts of alcohol on the night and that he may have been given an object by one of his companions before attacking Mr Brunlehner.

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