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The digital guru who helped Donald Trump to the presidency

Many of the "Tech Gods" were dismayed when Donald Trump - who holds a very different worldview - won the American presidency. But did they actually help him to win?

A key insider from the Trump campaign's digital operation - Theresa Wong - unravels for the first time the role played by social media and Facebook's in getting Trump into the White House.

Jamie Bartlett learns how Facebook's vast power to persuade was first built for advertisers, combining data about our internet use and psychological insights into how we think.

Watch Secrets of Silicon Valley on BBC Two, Sunday 8pm