 Complete the following phrase:  Khan was elected Mayor of London at the 2016 mayoral election, defeating the Conservative candidate Zac Goldsmith, and resigned as an MP. As Mayor, he implemented the Hopper fare for unlimited bus and tram journeys for an hour, increased the cost and the area covered by the London congestion charge, and introduced new charges the ULEZ and the T-Charge for older and more polluting vehicles driving in the city. He also backed expansion at London City Airport and Gatwick Airport. He was a vocal supporter of the unsuccessful Britain Stronger in Europe and Peoples Vote campaigns for 