With the entire political establishment massed against them and the bookmakers giving them no hope, the Leave campaign faced what many thought was an impossible battle to take Britain out of the European Union.

But election data published yesterday has provided a window into how Vote Leave upset the odds to land a sensational victory in last year's EU referendum.

While the Remain camp boasted of their success in reaching out to millions of people on Facebook, home to the millennial voters who would be expected to back Britain staying in the EU, it has emerged that the Leave campaign spent nearly half of its cash on a secretive consultancy firm that helped win the social media battle.