Undercover filming of illegal gases being sold in London

A BBC investigation has uncovered a black market in highly polluting greenhouse gases, which are being smuggled into the UK from Eastern Europe.

The gases - called hydrofluorocarbons (HFCs) - are being illegally advertised on and sold via social media.

The BBC found them openly advertised for sale on social media across the UK and tracked them down, being sold from a home in London.