Harry Potter first edition which was about to be sold for 50p at a car boot sale is expected to fetch £50,000 at auction.The rare book – one of just 500 hardback copies of Harry Potter and the Philosopher’s Stone – was found gathering dust on a bookshelf.Charlotte Rumsey, 28, was helping her mum Karen, 59, do a clearout of old books at her home in Blackpool when she came across the JK Rowling classic.