To create the YouGov election model we conducted more than 300,000 interviews, and then got two great data science brains — Ben Lauderdale of the LSE and Doug Rivers of Stanford — to apply our results to the Office for National Statistics map of Britain.

For two weeks our model was describing one reality, and everyone else — technical experts, gurus, field operatives, media pundits — were describing a totally different reality. We pushed and pulled the data in every direction to find the flaw, but we couldn’t find one. All the while we were being attacked from every direction.

The Conservative campaign strategist Jim Messina tweeted: “Spent the day laughing at yet another stupid poll from @yougov.” He mistakenly used the word “poll” because