The head of one of Germany’s most august noble families is suing his son for control over a spectacular Gothic revival castle and a stately city residence.

The Welfs, also known as the Guelphs, were once among the foremost medieval dynasties in Europe, ruling large parts of what are now southern Germany and northern Italy, including Tuscany, Bavaria and Saxony.

They were later the electors and kings of Hanover and ruled Britain and Ireland from the accession of George I in 1714 to the start of Victoria’s reign in 1837. They lost their last German royal title in 1866 but retain a substantial portfolio of properties, the best known of which is the 135-room Marienburg castle near Hanover, built in 1867 and sometimes likened to the famous Neuschwanstein castle in Bavaria.

Ernst August is accused by his father of “base ingratitude.”

Marienburg castle is now at the heart of a legal dispute between the patriarch of the family, Ernst August, prince of Hanover, and his son, also Ernst August, the Duke of Braunschweig and Lüneberg.

In the mid-2000s the older Ernst August, now 67, transferred Marienburg castle, a mansion in Hanover and the nearby Calenberg estate to his son. The son, 37, sold off part of the Calenberg lands and in 2018 announced that he was selling Marienburg castle to the government for a symbolic €1.

This was not purely altruistic. The castle has been largely untouched since the late 19th century and the cost of renovations is estimated at $32.8 million. It is visited by about 200,000 tourists a year but keeping it open has drained the family coffers, even though the Welfs sold valuables worth $53.5 million through Christie’s in 2005.

He was selling Marienburg Castle to the government for a symbolic €1.

The younger Ernst August said the sale of the castle was a “historic turning point” for the Welf family that would preserve it for the public. The Bundestag has already voted to contribute $16.5 million towards the cost of the necessary building work.

About 100 paintings and other artifacts from the castle, valued at a total of $2.4 million, have been handed to Hanover’s state museum and another $7.3 million worth of treasures have been placed in the possession of an art foundation. The father, a great-grandson of Kaiser Wilhelm II and a distant cousin of the Queen, was deeply aggrieved.

Ernst August, the estranged husband of the Princess of Monaco, has been described by the German press as the “party prince” and the “brawling prince,” owing to his well-publicized drunken escapades.

The state court in Hanover recently disclosed that the father had filed a lawsuit against his son to try to regain the properties, accusing the younger Ernst August of “base ingratitude” and “gravely violating the rights, legal entitlements and interests” of his father.

Court papers allege that the son tried to seize control of the estates “behind his father’s back” and illegally appropriated some of the family’s paintings, sculptures and antique coaches from a library and museum.

The father also claims to have been cut off without financial support and left to live in a “forest lodge” in Austria despite illness.

The younger Ernst August said the case was without merit and he was confident that it would be dismissed. “All the arguments in this lawsuit have already been refuted in an out-of-court settlement,” he told Der Spiegel. “Against this background we are relaxed about any dispute in court.”

No date has yet been set for a hearing.

Oliver Moody is a Berlin-based journalist for The Times of London