After days of speculation, Cornerstone imprint Arrow Books this afternoon confirmed 647,401 copies of Grey had been sold in the UK, in physical and e-book editions in the first three days since it was released on 18 June.

The previous first-week record in the UK was set by Dan Brown’s The Lost Symbol, which sold just under 551,000 copies in the five days following its launch. 

Managing director of Cornerstone, part of the Penguin Random House Group, Susan Sandon, said: “We've had magnificent support from across the trade. The excitement and enthusiasm that Grey's publication has generated is totally irresistible and I am delighted with these early results.”

Grey follows the same plot as the first book, Fifty Shades of Grey, but from the point of view of millionaire, Christian Grey, rather than that of his ingénue lover Anastasia Steele.

It is understood to have been printed at CPI's Mackays site in Chatham, Kent.

Although CPI lost the Penguin Random House contract to St Ives Clays in January, the publisher's titles are not set to move until later this year and the Grey job represents a late boost in the long relationship between the publisher and the printer. 

The loss of the contract was a blow to CPI UK, which said it was partly responsible for the group closing its Reading-based Cox & Wyman business.

Cornerstone has also been forced to deny it reported the theft of one of the first printed copies of Grey as a publicity stunt.

The Daily Telegraph reported only a handful of people had access to an Essex warehouse where copies of Grey were being kept after being printed in Kent, but a security check on 8 June found that a package had been ripped open and a copy taken. Penguin Random House then reported the matter to the police.

However a statement by Kent Police said there was “no evidence… to suggest an offence has been committed”.

Unlike Fifty Shades of Grey, which was serialised on a writers’ website before being sold to Penguin Random House, the publication of Grey caused a sensation across the media spectrum.

Author EL James made the announcement via Twitter, Facebook and Instagram posts on 1 June and the book rushed to the top of the online sales rankings, before going on sale in physical form on 18 June and prompting extensive coverage in the news media.

Neither CPI nor Cornerstone was willing to comment on print runs.

US publisher Vintage Anchor last night announced sales of over 1.1m in 4 days across its paperback, audio and e-book editions.

The Fifty Shades trilogy – Fifty Shades of Grey, Fifty Shades Darker and Fifty Shades Freed – has now sold more than 125m copies worldwide.