Fans of Harry Potter snapped up just over 2m copies of the new novel on its first day of release, 16 July.
Bloomsbury publicity director Katie Bond said the company was extremely grateful to Bungay-based St Ives subsidiary Clays.
She said the firm had carried out one of the most extraordinary print jobs under some of the most difficult circumstances, given the pre-publication media hype.
Speculation had surrounded the printing of the book, with The Sun naming Arvato subsidiary Druckerei GGP in Germany as the printer two months ago.
However, Bond said the German firm had produced an English language version for the German market, with Clays, who printed all the previous Harry Potter novels handling the UK market versions.
Although the UK edition of the novel was printed on 30% Forest Stewardship Council (FSC) certified paper, Bond said the publisher would not be providing details about the manufacturer or paper grade.
But Bond said there were encouraging signs that more Bloomsbury titles would be produced on FSC paper.
Story by Andy Scott
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