The "Up All Night" protests that are sweeping France are increasingly being marred by violence and police have warned the organisers not to let their peaceful cause be hijacked by troublemakers. The "Nuit Debout" demonstrations began in March in opposition to the government's proposed labour reforms, but the movement has now embraced a range of grievances and begun to take on a revolutionary feel. In recent days, after up to 3,000 predominantly young demonstrators have occupied the giant Place de la Republique square in Paris each evening, small groups of hooded youths have moved in, apparently determined to clash with...