Donald Trump's 2016 presidential campaign relied on data unethically harvested to build psychographic profiles of voters and manipulate their behaviour.

Trump's campaign team used Google, Snapchat, Twitter, Facebook and YouTube to micro-target US voters with carefully tailored messages about the Republican nominee across digital channels.

Intensive survey research, data modelling, and performance-optimising algorithms were used to target 10,000 different ads to different audiences in the months leading up to the election.

Earlier, Cambridge Analytica had harvested millions of Facebook profiles of US voters, in one of the technology company's biggest ever data breaches, and used them to build a powerful software programme to predict and influence choices at the ballot box.

The incident highlighted concerns about the manipulation of public opinion using data, AI and algorithms, and the privacy implications of the covert use of personal data for political purposes. 

It also raised questions about the connection between data-driven ads and democracy, and whether it is fundamentally toxic.