The author wrote to eight-year-old Christopher Howard in 1961. Now, Mr Howard from Kent has decided to sell the letter after keeping it for sixty years.

The private letter, hand-written by fountain pen on headed paper, displays the author’s Oxford address at the time and his phone number, BBC News reports.

It will be offered for auction in Royston, Hertfordshire, on 12 April with a guide price of £8,000-£10,000.