A major new campaign of disinformation around Brexit, designed to stir up UK ‘Leave’ voters, and distributed via Facebook, may have reached over 10 million people in the UK, according to new research. The source of the campaign is so far unknown, and will be embarrassing to Facebook which only this week claimed it was clamping down on ‘dark’ political advertising on its platform. Researchers for the UK-based digital agency 89up, allege that “Mainstream Network” — which looks and reads like a ‘mainstream’ news site but which has no contact details or reporter bylines — is serving hyper-targeted Facebook advertisements aimed at exhorting people in Leave-voting UK constituencies to tell their MP to “chuck Chequers”.