After a stint as a significant Tory donor, he later sought to ascend to the role of Conservative Party treasurer.

However, he stood down shortly after his appointment in 2010 amid scrutiny of his tax affairs. Prior to that, he had been a long-term tax exile in Guernsey before returning to the UK.

The Tory treasurer bust-up prompted closer scrutiny of Rowland’s business affairs, and raised questions about the close ties between the Duke’s role as former international trade envoy and Banque Havilland’s bid to lure wealthy clients.

Described in some reports as an “unofficial door-opener” for Rowland and Banque Havilland, the Duke’s globe-trotting role offered a useful way to win new clients.

The relationship also led to Mr Rowland paying off a £1.5m loan taken out by the Duke with Banque Havilland, Bloomberg reported.

Although Rowland owns the bank, he has held no formal role in it. A number of family members, including his sons Jonathan and Edmund, have held directorships or senior positions in the past.

Harley Rowland, a 44-year-old former millennium hedge fund manager, is currently the family’s representative on the board.

Following the ECB’s move, Banque Havilland has stopped taking deposits and payments and the CSSF has been forced to step in to wind down the bank in orderly fashion.

Around 200 staff who work in Luxembourg are likely to lose their jobs although they remain in post awaiting more information.

Havilland’s branches in Liechtenstein and Switzerland have also been placed into voluntary liquidation ahead of the ECB’s decision.

The only survivor of the Havilland empire is likely to be its branch in Monaco, with the 20-person office set to be sold to a buyer before the end of the month, according to a source familiar with the matter.

Banque Havilland declined to comment and referred to a prior statement. Rowland could not be reached for comment. The ECB declined to comment.