The Labour Party leadership of Jeremy Corbyn began when Jeremy Corbyn was elected as Leader of the UK Labour Party in September 2015, following the resignation of Ed Miliband after Labour’s defeat at the 2015 general election. Disillusioned with a lack of a left-wing voice in the 2015 leadership contest, Corbyn stood on an anti-austerity ticket.
https://en.wikipedia.org/wiki/Labour_Party_leadership_of_Jeremy_Corbyn