General election: Why did political pollsters get it so wrong?
Published polls ahead of the 2015 general election proved to be a bad prediction of the results.
The Conservatives won the election, with a majority of 12 seats, but polls ahead of May 7 had suggested they would not win a majority.
Labour's election pollster has said public polls "showed a much more favourable position for Labour than we were finding in our internal data" both before the campaign and during it.
Chris Cook reports for Newsnight.