Celia Fernie's initial impression was that the woman identifying herself as Mrs Murray was a "very nice lady" with a loving family - someone who would make a good home for one of her greyhounds.

It was only when she asked for a £30 donation to Greyhound Rescue Fife, which the 61-year-old runs with her husband, Jimmy, near Kirkcaldy, that she realised she had been dealing with the world's most famous children's author.

At the bottom of a cheque for £1000 was the signature millions of Harry Potter fans would die for. "When I looked at the cheque I couldn't believe it. The first thing I noticed was the amount she had made it out for," Mrs Fernie said yesterday.

"Then I spotted her name and realised who it was. I just said Oh, I didn't recognise you,' and she just smiled politely. She was a lovely woman - the whole family were very nice."

Pictures showing JK Rowling and her new dog, Sapphire, have since been posted on the Fernies' website under a Harry Potter Page link where the Edinburgh author is described as a "very private but wonderful lady".

Joanne Murray, it transpires, is the name JK Rowling uses when she wishes to avoid the burdens of her celebrity status. She is married to Neil Murray, a GP with whom she has three children.

Before adopting Sapphire, a retired racing dog, the family visited the rescue centre with their other dog, a Jack Russell called Butch, before choosing the four-year-old bitch.

But this was only after a telephone grilling by Mrs Fernie to establish whether Rowling would make a suitable dog owner.

"I always ask a person a bit about their lifestyle - what size their house is, do they have a garden and quite importantly does it have a wall at least 6ft high, because I would hate for the dog to get out and run off," Mrs Fernie recalled.

"She sounded very genuine," she added.

"I could see Sapphire was going to a good home. Now I know just how good," she said.