Harry Potter first editions have become a profitable business, with a copy of Harry Potter And The Chamber of Secrets, which was bought for “a penny plus postage” on Amazon, will be sold at auction on Thursday with a price estimate of £1,800-£2,500.

It is being sold in Hansons’ Fine Art & Library Auction at Bishton Hall, Wolseley Bridge, Staffordshire.

In October Hansons sold two rare first editions of Harry Potter and the Philosopher’s Stone for £57,040. Only 500 were printed and most went to schools or libraries.

The seller on Thursday is a Mark Cavoto, 51, a businessman from Buxton, Derbyshire, and father of five who began buying Harry Potter books for his daughter, Holly, who is now 25.

Over the last 10 years, Cavato, said to be the biggest collector of Harry Potter books in the world, has bought and sold around 3,000 copies.

Cavato explained: “When Holly was a child, she loved Harry Potter books and started her own collection. About 10 years ago, we decided to sell some of her older books and three of them were snapped up within 20 minutes on eBay for £9.99 each.

“It turned into a business. I started buying Harry Potter books for next to nothing at charity shops and online. I turned them into sets relating to the different editions and sold them on eBay. I currently have around 120 Harry Potter books on eBay.”

He recalled his chance discovery of the book signed by J. K. Rowling: “I was buying around 10 Harry Potter books a day and Holly liked to open all the Jiffy bags. One day she glanced at a book she’d just opened and said, ‘This is no good, it’s got ink on it’.

“She carried on opening the others then went back to it. She stared at me and said, ‘Oh my God, it’s been signed by J K Rowling — and it’s a first impression’.

“I thought she was messing with me but it was true. It was signed, ‘To Alexandra (again!) J. K. Rowling’, and was a 1998 hardback first edition of Harry Potter and the Chamber of Secrets, the second novel in the series.”

Another sale gave him enough money to start a second business, which helps people source items that are missing to complete their collections, from model ships and trains to Star Wars figures and ships.

He said: “I bought an edition of Harry Potter and The Philosopher’s Stone, the first

J.K. Rowling book, from the second print run. It’s as rare as the 500 books in the first print run. I decided to advertise it for £5,000 and an Australian dealer offered £4,600 for the book. I’d paid a penny for it. I snapped his hand off and used the money to start Partworks Collectables. I help people complete their collections.”

For that reason, in Hansons’ sale, Cavoto is parting with a set of books consisting of the first 10 hardback editions of Harry Potter and the Chamber of Secrets, estimate £600-£800.

He is also selling six copies of the first edition hardback of Harry Potter and the Philosopher’s Stone, the first novel in the series published in 1997.

These include the third, fourth, fifth, eighth, ninth and tenth impression — but not the holy grail for collectors, the first impression of the first book.

Cavoto revealed: “I keep around 1,100 in a warehouse and another 400 at home. They have taken over my office. But this isn’t just about money. The whole thing has been a bit of fun for me and my wife.”

Jim Spencer, books expert at Hansons, said: “J.K. Rowling rarely signs so the book featuring her signature deserves to do really well.

“Another client is selling a copy of Harry Potter and the Deathly Hallows signed by J.K. Rowling.

“It comes complete with goody bag from the signing event including a deflated balloon. The Harry Potter magic lives on.”