The first book in the Cormoran Strike series, the Cuckoo’s Calling, was reviewed by fellow writers including Val McDermid and James Patterson, before Rowling had been revealed as the true author.
Rowling, 52, wrote to thank them in fake handwriting but later apologised for fooling them when her cover was blown.
She said: “I wasn’t trying to trick anyone or fool anyone. I was just aware that I would be lucky to get away with it for many years. But I certainly hoped I’d be able to get three books out of Robert before anyone knew.”
Explaining why she chose to write under the pseudonym, Rowling said: “I wanted to go back to the beginning. I wanted it to just be about the writing.”
The Cuckoo’s Calling, about private investigator Cormoran Strike, has now been adapted into a BBC One drama with Tom Burke in the lead role and Holliday Grainger as fellow character Robin Ellacott.
The final instalment of the three-part series airs tonight.
And Rowling revealed that the BBC were interested in the Galbraith books even before they knew the author’s true identity.
It meant she knew she would soon have to come clean.
Rowling added: “We had a call from the BBC. That presented ‘Robert’ with his biggest problem which is a really nice problem to have – but things became difficult to sustain quite quickly.”