Schoolchildren were delighted when a best-selling author dropped in.

Pupils at the Headington Preparatory School, in London Road, Headington, Oxford, thought they were attending an assembly about their favourite author, Jacqueline Wilson.

But they were "gob smacked" when the author, who created children's favourite Tracy Beaker, walked on stage.

Headteacher Andrea Bartlett said: "It was absolutely fantastic. All of the children were completely taken by surprise - they didn't have a clue.

"We told them that we were doing an assembly on Jacqueline and got them to bring in their favourite books by her as we knew she would do a book signing."

The author spoke to the children for more than 45 minutes about what it is like to be an author, where she gets her ideas from and how she creates her characters, before answering questions.

Miss Bartlett said: "The children were completely spellbound by what she had to say and asked her lots of questions, which she was more than happy to answer."

Following the questions, Ms Wilson signed copies of her books for the children to keep as mementoes.