Best-selling author J.K. Rowling revealed how she broke down in tears during the completion of her final book in the Harry Potter series.

She also tells interviewer Jonathan Ross how she changed the last word in Harry Potter and the Deathly Hallows at the eleventh hour.

When I finished one chapter near the end I absolutely howled, she told the BBC television presenter.

She finished the book alone in a hotel room.

I was sobbing my heart out -- I downed half a bottle of champagne from the mini bar in one and went home with mascara all over my face. That was really tough.

The Deathly Hallows is the seventh and final book about the schoolboy wizard Harry Potter and his Hogwarts friends.

The plots have taken a darker turn and Rowling has in the past revealed that she would kill off at least two of the main characters.

When asked by the chat show host whether the word scar was still the last word in the book, as had been reported, she said: Scar? It was for ages, and now it's not.

Scar is quite near the end, but it's not the last word.

Harry Potter has a lightning bolt scar on his forehead as a result of a failed curse by the wicked wizard Lord Voldemort.

Rowling also revealed that the character Harry Potter was totally imaginary and not based on anyone.

His red-haired pal Ron Weasley was a lot like her oldest friend Sean though, she confessed.

More than 325 million copies of the first six books have been sold worldwide, helping to turn Rowling into the first dollar-billionaire author.

An all-British cast seemed to be a point of pride for her as she admitted it had been a hell of an achievement.

Stars who have appeared in the five films, including the latest Harry Potter and the Order of the Phoenix, include Maggie Smith, Robbie Coltrane, Julie Walters, Richard Harris, Imelda Staunton, Alan Rickman and Ralph Fiennes.

The film had its premiere in London this week.

The Deathly Hallows appears on the bookshelves on July 21, but 1.6 million copies have been pre-ordered online.

* The Jonathan Ross interview will be broadcast on BBC One on Friday, July 6.