Influence of leaders show revealed by Leeds University research

A study for the Electoral Reform Society found the programme - which saw Theresa May and Jeremy Corbyn face an audience days before the country went to the polls - swung a third of viewers’ votes. Researchers at the University of Leeds found 34 per cent of 4m viewers said the show helped decide their vote. They held a poll of more than 2,500 people before and after they watched the programme.

Mr Corbyn gave the best performance, the study found, with the strongest swing to the Labour leader among younger viewers - many of whom were undecided before tuning in. The research saw a surge in youth engagement in politics, with 80 per cent of 18 to 24-year-olds saying they were interested, compared to 50 per cent in 2015.

Darren Hughes, chief executive of the Electoral Reform Society, said the study showed the importance of TV debates in UK general elections. He said: “This research is proof that televised election debates are good for our democracy.

“That over 80% of viewers said they talked about the QT special with their friends and family shows it has a positive impact on political engagement. And 40% said the programme made them more interested in the campaign. That’s good for all of us.”

He said the swing to Mr Corbyn suggested the programme “may have had an impact on the final result - particularly when just a few hundred votes in swing seats shifted June’s outcome”.