Transformers wreaks box office revenge
The impressive opening is the biggest for a film in British cinemas this year, beating big-budget sci-fi rivals Star Trek and Terminator Salvation into submission.
Michael Bay's sequel to 2007's Transformers reunites lead actors Megan Fox and Shia Labeouf.
Last week's number one The Hangover slipped one place in this week's ratings to number two, while family comedy Night At The Museum 2 clinging on to the third-place spot.
Previous number one Terminator Salvation fell to number four while Dan Brown thriller Angels & Demons held steady at five.
LaBeouf recently hinted to the Press Association that the next sequel to Transformers will be "darker" than its two predecessors.
Although a third instalment has not yet been confirmed, he told the news organisation "something crazy will happen, someone has to die".