Radio 4 is to test the forbearance of its famously loyal band of listeners by clearing the schedules for an uninterrupted, eight-hour reading of JK Rowling's first Harry Potter novel on Boxing Day.

The marathon recording of Harry Potter and the Philosopher's Stone, read by Stephen Fry, will start at noon. The somewhat eccentric scheduling tactic came about because of Ms Rowling's insistence that the book be read unabridged and in one go.

Helen Boaden, the controller of Radio 4, said the broadcast could become an event that listeners would recall for years to come: "What we're doing is a radio experience. I would like there to be a generation of children in their 20s who will look back and remember listening to the radio on Boxing Day, because Harry Potter is part of their imaginative landscape."

Ms Boaden confessed yesterday to having been "taken aback" when Ms Rowling's agent, Christopher Little, revealed that the only way of broadcasting a Harry Potter reading on the radio was to play the full Fry recording, which is available commercially and is the only one authorised by the author. She "gulped" when she realised the terms were non-negotiable, and told Mr Little that she would have to think about it. "But when I was coming back on the 94 bus I thought: 'I know how we'll do it.' "

So, Radio 4's normal Boxing Day schedule - which includes Desert Island Discs, a play and the shipping forecast - will be broadcast on longwave, while listeners to FM will be treated to Harry Potter.

Only Radio 4 would have the "bottle" to take such an unusual step, Ms Boaden said. "Radio 4 has the confidence, the tradition, the backbone if you like, to throw the normal rules in the air just once in a while and surprise everyone. I think that's part of our job."

Ms Boaden, who has been in her post for eight months, said she was convinced of the wisdom of the move when she recalled giving her nephew an audio version of the book last Christmas: he disappeared to his room for hours. "I just thought the power of story-telling should never be under-estimated," she said.

Few listeners would concentrate on the recording for the full eight hours, she predicted, but many families might keep it on in the background, or in children's bedrooms, all day. "I'd be amazed if people listened intently for eight hours. I think there will be people who keep it on all day and dip, mentally, in and out."

Fry, who is filming in Spain, said yesterday that he was delighted. "Reading Harry Potter books out loud is more fun than I feel a single human being could ever deserve. It's like swimming in chocolate."

Ms Boaden, who is keen to attract younger listeners and has already announced plans to revive a dedicated children's programme, said Fry was the ideal choice to read the book. "I felt that him reading Harry Potter on Radio 4 might be a way of bringing a new generation of children ... to the magical experience of listening to speech radio and seeing the pictures in their heads."