Rare Harry Potter goes under the hammer

The auction house Sotheby's is selling a first edition copy of Harry Potter and the Philosopher's Stone which features comments and drawings from its author JK Rowling.

The book, which goes under the hammer on Tuesday evening, is expected to fetch about £20,000.

A number of other works are also being auctioned, including a first edition of Hunter S. Thompson's Fear and Loathing in Las Vegas and Roald Dahl's Matilda.

Dr Philip Errington from Sotheby's explains the significance of the Potter book.