What is behind the diesel cars emissions scandal?

All 93 vehicles tested in Germany and UK exceeded EU-set limits on air quality and pollution in real-world situation

The air pollution scandal that hit front pages around the world last year with VW's admission it had been cheating emissions tests has got much bigger.

A UK government-sponsored trial launched in the wake of the VW revelations has found that every single one of the diesel-fuelled vehicles tested had higher emissions of nitrogen oxide pollutants than permitted under EU laws. For some models emissions were 12 times the legal limit.