Exit polls and the man behind the maths
Media playback is unsupported on your device
Video

General Election 2017: The statistician predicting winners

When the polls close on 8 June, the result of the general election could be foreseen before votes are even counted.

Prof David Firth, a statistician at the University of Warwick and Alan Turing Institute, joined forces with politics professor John Curtice, of Strathclyde University, on exit polls for the 2005 election.

After they got the result right, the process was repeated in 2010 and 2015.

Prof Firth, who devised the statistical methods used, said at first people didn't believe it would work.