Justin Trudeau was spotted at a Katy Perry concert in Montreal on Wednesday night, days after the pop star and the former Canadian prime minister were seen dining together at a restaurant in the city. A video of the concert shows the former Liberal Party leader, 53, singing along as Perry performed her song Dark Horse.The Firework singer, 40, is currently on her Lifetimes Tour and is set to perform in Quebec City on Friday.Earlier this week, Perry and Trudeau enjoyed a meal at Le Violon in Montreal's Le Plateau neighbourhood.