Diplomat Expulsions: 'What are the rules now?'

Russia has promised a tough response to the decision by more than twenty countries to expel its diplomats in response to a nerve agent attack in the UK.

Also in the programme: reports of a mystery train arriving in Beijing from North Korea - we ask, who's on it? and; can plastic prevent coral bleaching?

Picture: The President of Estonia Kersti Kaljulaid. Credit: AFP/Getty Images.