The billionaire Barclay brothers on Wednesday asked the High Court to sweep the vestiges of feudalism from the tiny Channel Island of Sark, in the latest move in a battle over how the Crown protectorate should be governed.

The twins, who own a fifth of the island in addition to their interests in London’s Ritz Hotel and The Daily Telegraph, have been pushing for constitutional modernisation since buying the neighbouring isle of Brecqhou 15 years ago.