A rare edition of the first Harry Potter book is expected to fetch up to £30,000 at auction after it was kept in a briefcase for more than 20 years.

The 1997 Harry Potter And The Philosopher’s Stone hardback edition was gifted to a Lancashire family who locked it in a briefcase for safekeeping and planned to keep it as a family heirloom.

After hearing about another first edition of the first book in JK Rowling’s boy wizard series selling for £28,500 in July, the family, who wish to remain anonymous, decided to sell it.

“We thought, ‘what’s the use of our books lying around in a briefcase when a collector might treasure them?'” they said in a statement on Monday.

The rare edition, published with two errors, will go under the hammer at Hansons Auctioneers on October 10 with a guide price of £25,000 to £30,000.

A dozen first edition Harry Potter books are for sale at Hanson Auctioneers (Hansons/PA)A dozen first edition Harry Potter books are for sale at Hanson Auctioneers (Hansons/PA)

Associate director Jim Spencer said first edition hardbacks of Harry Potter And The Philosopher’s Stone are the “holy grail” for collectors because so few were printed.

“I couldn’t believe the condition of it – almost like the day it was made. I can’t imagine a better copy can be found,” he said in a statement.

“This new discovery is scarcer than the previous find, which was a former Staffordshire library book. It deserves to fetch much more.”

Only 500 copies were published in the tale’s first print run, with 300 of these sent to libraries, Hansons said.

The book will be among 12 Harry Potter first editions for sale at Thursday’s auction, including one signed by JK Rowling.

Hanson Auctioneers expect that in total the books will sell for between £35,000 to £40,000.