Erotic novel 'Fifty Shades of Grey', dubbed "mummy porn" by the media, has become the fastest paperback to reach one million sales in Britain.
The EL James novel, the first in a trilogy, took just 11 weeks to reach the milestone, 25 weeks faster than the previous record holder, Dan Brown's 'The Da Vinci Code', according to figures from publishing tracking company Nielsen BookScan.
It also beat its own seven-day record for an adult paperback, shifting 397,889 copies in a week.
According to Random House publishers, global sales for the series is now in excess of 20 million, with North American sales comfortably topping 15 million.
'Fifty Shades of Grey', about a relationship between naive literature student Anastasia Steele and manipulative entrepreneur Christian Grey, was first published in 2011 and was Ms James's first novel.