In August 2018, Spanish authorities uncovered a plot by anti-Brexit campaigners to assassinate leading Brexiteer and now favourite to be Britain’s next prime minister, Boris Johnson. Or did they?

Less than two weeks before pivotal elections for the European Parliament, a constellation of websites and social media accounts linked to Russia or far-right groups is spreading disinformation, encouraging discord and amplifying distrust in the centrist parties that have governed for decades.

Foreign Twitter accounts have recently tried to influence the debate around Brexit, with pro-Leave tweets receiving the most support, researchers say.

The watchful volunteers have recruited an international force of thousands to help stem disinformation, writes Kim Sengupta.