HARRY POTTER creator JK Rowling is planning to transform historic Stirling Castle into her famous school of witchcraft and wizardry, Hogwarts. She is hosting a £250-a-head Halloween charity ball at the castle, which promises to be one of the most glamorous events of the year.

Rowling, 36, is patron of the Multiple Sclerosis Society in Scotland, who will receive all the profits from the bash, and selected the top-secret guest list herself.She's even sent out a cheeky letter with the invite, gently poking fun at the schoolboy wizard character that has made her a multi-millionaire. She asks guests if they are planning to celebrate Halloween by "hiding from the hordes of Harry Potter lookalikes banging on your front door? "Or would you prefer to come to a stunning Celtic Halloween Ball and allow me to apologise in person for inflicting so many round, plastic spectacles on the world?"

No expense has been spared for the black-tie ball, which is sponsored by the author's publisher, Bloomsbury. Rowling promises her guests "a truly magical night without a single badly-drawn-in-lipstick lightning scar".

On arrival, guests will be greeted by witches, wizards and magicians, while the music will be supplied by pipers, clarsach and flute players. And, just like Hogwarts, burning torches will decorate the castle's Great Hall, where a four-course dinner will be served, before a charity auction. But there is a serious side to the ball, on November 1. Rowling's mother Anne died from multiple sclerosis in 1990 after a long battle with the illness. In her letter, Rowling writes: "Over 10,000 people have MS in Scotland, making it the MS capital of the world, yet the level of research and care generally available here can best be described as appalling. "My mother died of MS at the age of 45 and this is therefore a cause that is very dear to my heart." Mum-of-one Rowling has admitted her mother's death is responsible for the fact Harry Potter is an orphan and the pivotal role death and bereavement play in her books.

And she says she still cries when thinks of her mother. She said: "I miss her almost daily and I feel desperately sad for all she missed. "She died before either of her daughters married, never met her granddaughter and I never told her about Harry Potter. I still can't write about her without crying."

JK Rowling's spokeswoman last night confirmed the glittering event was to take place, and added: "Jo has written a private letter, and the event was her idea. "It's something that's been discussed right from the start of her involvement with She's very much a hands-on patron." She refused say who had been invited, adding: "It's a private invitation list and will be a fairly exclusive event."

Rowling, who married 30-year-old doctor Neil Murray on Boxing Day last year, has already helped organise the Scottish charity premiere of the film Harry Potter and the Philosopher's Stone.

The event raised money for the MS Society and Maggie's Cancer Care Centres in Scotland.