The solicitor who let slip the pseudonym of Harry Potter author JK Rowling has been ordered to pay a financial penalty of £1,000 for breaking confidentiality rules.

The Solicitors Regulation Authority today confirmed that Christopher Gossage, a partner at London firm Russells Solicitors, has also been issued with a written rebuke.

In July, the firm confirmed it was the source of leaked information about the true identity of ‘Robert Galbraith’, the writer of crime novel The Cuckoo’s Calling.

Rowling had wanted to keep the secret for longer but her pseudonym was revealed in the Sunday Times after Gossage told his wife’s best friend during a private conversation.

Russells’ statement said while Gossage accepted his own culpability, the disclosure was made ‘in confidence to someone he trusted implicitly’.

It added that the leak was not part of any marketing plan and neither Rowling nor her agent were involved in any way.

The firm has since apologised and made a ‘substantial charitable donation’ to the Soldiers’ Charity as a result of legal action brought by the author.

The SRA’s sanction notice said Gossage had breached two of the SRA principles 2011 and failed to achieve outcome 4.1 of the code of conduct.

The book itself became the week’s best-selling novel on Amazon following the leak and a sequel is expected to be published next year.