Yellow vests are 'gatecrashing' traditional May 1 labour and anarchist protests

Thousands began rallying for May Day in Paris on Wednesday, with a heady mix of labour unionists, "yellow vest" demonstrators and hardline troublemakers expected to turn out in a test for France's zero-tolerance policy on protest violence.Authorities have warned that this year's marches could be tense, coming barely a week after leaders of the yellow vest anti-government movement angrily dismissed a package of tax cuts by President Emmanuel Macron.And with trade unions hoping to raise their profile and thuggish "casseurs" vowing to turn Paris into "the capital of rioting", the government moved to deploy security on an "exceptional scale" throughout the capital.