Roger Quirk, 44, admitted three counts of breaking the Data Protection Law after taking hundreds of pages of files when he left his position as senior client partner at Coutts for a new role in London two years ago.

According to Jersey’s deputy data protection commissioner, Paul Vane, it was the first prosecution of its kind on the island.

He said the case “highlighted a growing trend” and that there were “three similar investigations on the books at the moment”.

This kind of misuse of personal information is a serious offence, and we will use our powers to take action against those who break the law. A conviction for breaking the Data Protection Law doesn't look very good on the CV of anyone who wants to work with sensitive information, and we hope that this case will act as a warning,” added Vane.

Quirk, who left Coutts to work for the Swiss private bank Clariden Leu, was given an absolute discharge by the court, avoiding a fine or imprisonment. He did, however, have to return 300 pages of documents to Coutts’ Jersey branch.

Vane, who led the investigation, said the companies involved had “co-operated fully with the inquiry”.

“Coutts has taken all of the necessary steps in terms of data protection training and policies with its staff including Quirk,” said Vane and added, that Clariden Leu had taken immediate action when they were told their new employee had been approaching former clients from their offices.

Commenting on the investigation, a Coutts spokesperson said that "the protection of client data held with the bank is of vital importance to us and the Royal Court's actions are welcome."