The author was unmasked as the writer of a thriller - The Cuckoo’s Calling - written under a pseudonym Robert Galbraith, after a tweet exposed her as the writer. The twitterer, Judith Callegari, turned out to be  a close friend of the wife of Russells partner Chris Gossage.

Grovelling apology

The firm made a grovelling apology to the author ‘for the disclosure caused by one of our partners’ and said it had informed Ms Rowling’s agent when realising what had happened. ‘We, Russells Solicitors, apologise unreservedly for the disclosure caused by one of our partners, Chris Gossage, in revealing to his wife's best friend, Judith Callegari, during a private conversation that the true identity of Robert Galbraith was in fact JK Rowling.’

The statement went on to say: ‘Whilst accepting his own culpability, the disclosure was made in confidence to someone he trusted implicitly. On becoming aware of the circumstances, we immediately notified JK Rowling's agent. We can confirm that this leak was not part of any marketing plan and that neither JK Rowling, her agent nor publishers were in any way involved.’

Calm advice

Russells is a London’s West end firm specialising in the entertainment industry. Mr Gossage head up its corporate department. According to the firm’s website, he has ‘a reputation for clear and concise analysis as well as calm and thorough advice, preparation and negotiation in the highly pressurised world of corporate transactions.’

In a statement, Ms Rowling said ‘To say that I am disappointed is an understatement. I had assumed that I could expect total confidentiality from Russells, a reputable professional firm, and I feel very angry that my trust turned out to be misplaced.’