Labour leadership: 'Political earthquake' if Jeremy Corbyn wins

The Labour Party is preparing to announce its new leader after a turbulent three-month campaign.

Left-wing anti-austerity MP Jeremy Corbyn, an outsider when he first entered the race, is seen as favourite.

He is up against former ministers Yvette Cooper and Andy Burnham and shadow minister Liz Kendall.

The BBC's Chris Mason reports.