Waterstones’ sales of the new Harper Lee novel were off to a “storming start” and are comparable to those of the final Harry Potter novel.

The book retailer opened stores in Piccadilly, Glasgow, Newcastle and Leeds at midnight to capitalise on today’s launch of Go Set a Watchman.  

Waterstones managing director James Daunt believes the retailer will sell between 30,000 and 40,000 copies of the book today and sales are oustripping the new Fifty Shades of Grey book threefold.

He said: “It is going to be absolutely enormous. The thing about this is it has real legs to it and the pre-orders have not really been picked up yet.

“It is a real humdinger for us. We were ready and waiting for this one, it is the most exciting thing we have had so we have an extreme number of copies in the business and nowadays we have the ability to resupply so will get a lot back in tomorrow.”

Daunt predicts a bumper weekend of sales on the back of the release of Go Set a Watchman.

He described the release of the Harper Lee novel as a “wonderful publishing sensation” which has come “just at the right time” because it is during a time when shoppers splash out on novels during the summer holidays.

Daunt expects Waterstones’ sales of the book would “comfortably march into five figures” in the coming weeks.