K Rowling has said she feels “very angry” after finding out her pseudonym Robert Galbraith was leaked by a legal firm.
The Harry Potter author was revealed as the writer of crime novel The Cuckoo’s Calling in the Sunday Times.
She found out the leak came from law firm Russells, whom she had assumed she “could expect total confidentiality from”.
“I feel very angry that my trust turned out to be misplaced.
“To say that I am disappointed is an understatement,” she said in a statement.
“A tiny number of people knew my pseudonym and it has not been pleasant to wonder for days how a woman whom I had never heard of prior to Sunday night could have found out something that many of my oldest friends did not know,” she added.
Russells Solicitors said it apologised “unreservedly”.
In a statement, it said the wife of one of its partners, Chris Gossage, had told her best friend, Judith Callegari, that Robert Galbraith was really Rowling.
The company said it was revealed “during a private conversation” adding “the disclosure was made in confidence to someone he trusted implicitly”.
It has been reported Ms Callegari subsequently revealed Rowling’s identity to a Sunday Times journalist via Twitter on 9 July.
Russells continued: “Whilst accepting [Gossage’s] 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.”