How did a small town in Wales where the EU has invested millions upon millions come to think “the EU does nothing for us”? Answering that question was what opened up the dark hole of micro-targeted propaganda that drove the Leave campaign, and turned feature writer Carole Cadwalladr into an investigative journalist.

People on the Leave side of Brexit make much hay of Carole's occasional errors in reporting. But that misses the point — and shows up the desperation to discredit her. Errors will occur in stories as complex as this, and her dogged determination to get at the truth of the matter has led to her becoming essentially both a tech reporter and an investigative journalist on the fly.

That's, at its heart, a pretty inspiring tale about someone finding a story, albeit a pretty hard to report one, and just not giving up.

(And yes, there are questions to be asked around why, for example, more mainstream tech reporting didn't glom onto this as a possible issue before it hit reality — but that then opens up the much larger issue of why so much reporting about Facebook was so positive for so long.)

And now we all need to ask: is this the future for all our democracies? Undermined by dark money running hidden ads, psychologically targeted to people’s vulnerabilities that nobody can track?

Sometimes the best journalism creates far more questions that it answers.

Take the 15 minutes to watch this video. It's well worth it.