When Oxfam’s specialist bookshop in Thame celebrated banned books earlier this year, Enid Blyton’s children’s stories were at the centre of their display.

Books by the author of Noddy and The Famous Five were banned for 27 years by BBC bosses, who dismissed her work as lacking literary value, until the ruling was lifted in 1963.

Now the discovery of a first edition of one of her stories at the shop in Cornmarket is expected to raise about £395 for the charity.

Last month a customer donated a box of old books to the shop and a volunteer picked out a first edition of The Castle of Adventure.

Published in 1946, the hardback in an unclipped dustwrapper has been valued at £395.

If it is not snapped up from the shop’s Christmas children’s book window display, it will be sold online.

Shop manager Dick Jennens said: “This first edition is a fantastic find for us – it’s the second novel in the Adventure series so a first edition is quite sought after.

“The book is in lovely condition and as it was published in 1946 the print run would not have been enormous because publishers were still subject to wartime paper supply restrictions.

“The book came in a mixed box of donated books.

“One of our researchers picked it out and put it to one side so that we could spend a bit of time researching its value. Most people either know what they are donating or they say ‘I hope you find something valuable’.

“It soon became clear that the book was worth quite a bit.

“Oxfam seems to attract volunteers with a high level of skill which means we don’t miss much or make too many mistakes.”

Mr Jennens added that Enid Blyton’s books were still collectable and popular with young readers.

He said: “It’s amazing to think that she was banned for about 30 years by the BBC.

“She is just such a great storyteller and can still get kids hooked on reading today – we will make The Castle of Adventure the centre of our new Christmas window display.”

The dustwrapper of the book, published by Macmillan, is illustrated by Stuart Tresilian.

Mr Jennens said £400 would buy 150 Oxfam buckets to help people in drought-ridden East Africa carry water or cover a tenth of the cost of drilling a new bore hole.

In November 2010, an anonymous donor brought into the store a first edition of George Orwell’s Animal Farm from 1945 valued at £995.

And in 2008, a copy of Graham Greene’s 1931 novel Rumour at Nightfall raised £15,000 at auction after it was spotted at the Oxfam bookshop in St Giles, Oxford.