Five major car brands have gone on trial in the UK over so-called dieselgate.
The class action lawsuit, involving 850,000 drivers, is being heard at the High Court.
It's been 10 years since dieselgate first came to light.
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That was the scandal which engulfed the Volkswagen group, later costing the company about £30bn in fines and compensation.
It was revealed in 2015 that the German carmaker had fitted so-called defeat devices to most diesel models - software that would give a false, low reading when the vehicles were undergoing emissions testing.
The bulk of VW's bill was paid out in the United States, where it was claimed that vehicles were emitting up