It’s almost hard to believe. Three years ago, Paris was the scene of a groundbreaking deal on climate change . Now, it is reeling from its worst riots in 50 years, ignited by a proposed tax on dirty fossil fuels.

What started as an online petition against rising fuel prices soon exploded into violent protest. Cars have been set alight, shops have been vandalised and four people have died in the past month. Prime Minister Edouard Philippe – who was scheduled …