Online political advertising is a black box and democracy should be worried

Companies are promising to sway the electorate using high-tech targeting of voters in ways that aren't easy to keep track of

As your mind wearily contemplates being exposed to yet another political campaign, are your dreams haunted by battle buses, billboards and TV debates? Or is it Facebook, YouTube, Twitter and Google?

On the evidence of last year's EU referendum, much of the campaigning, and much of the money spent on political advertising, will be online. And it will happen in a way that will be largely hidden from scrutiny by either the public or regulators.