Peter Rabbit: Loved by adults and children worldwide

Details of her fight against Peter Rabbit imposters are contained in previously unseen files.

Dozens of letters released by the Public Record Office show bootleg copies of her first book, The Tale of Peter Rabbit, flooded foreign markets during and after World War II.

America was the only country where Potter's original story was not subject to strict copyright and became the source for many of the unauthorised copies and stories written by other authors using the characters.

One pirated series of 13 books including titles such as How Peter Rabbit Went to Sea and Peter Rabbit and the Tinybits emerged from the United States.

In New Zealand, in 1946, a version called Famous Rabbit Stories was sold in Woolworth's, who withdrew the copies after being contacted by the authorised publisher Frederick Warne.

Even in 1949 fakes were still entering Britain. One letter to Customs and Excise said: "Our clients find...that in most cases the story is the same and the illustrations are definitely colourable imitations and quite often the exact characters in the same position as in their own publication."

Eventually, the publishers signed a Customs declaration banning the sale of the bootleg books in any country other than America.

The file was stamped "Put Away" on 30 May, 1949, where it has remained until now.

Bad start

Kensington-born (Helen) Beatrix Potter first created the character of Peter Rabbit in an illustrated letter sent to Noel Moore in 1893, based on one of her own pet rabbits.

After receiving rejections from at least six publishers, including Warne's, Miss Potter decided to have the book privately printed.

She ordered a run of 250 copies in December, 1901. A surviving copy is now worth up to �30,000.

A year later her book was accepted, launching a successful career as a children's storyteller.

Many of her stories centred on her farm in the Lake District, where she became one of the main benefactors of the National Trust.