More than a million legal claims against some of the world's leading car manufacturers over allegations their vehicles contained technology that allowed them to cheat emissions tests are set to be tried at the High Court on Monday.

Around 1.6 million motorists are taking legal action against more than a dozen manufacturers over claims that several diesel vehicles made from 2009 onwards contained "prohibited defeat devices" (PDDs).

The claim is the largest of its kind in English history, with the High Court previously told it is believed to be worth at least £6 billion.

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Those taking legal action either bought, leased or otherwise acquired a diesel vehicle made by one of the companies, with most living in England and Wales but some living elsewhere in the UK.

They claim that the PDDs installed in the cars allowed them to detect when they were being tested and alter the amount of harmful emissions produced, allowing them to pass.

The vehicles in the claims were made by Mercedes-Benz, Opel and Vauxhall, Nissan and Renault, Volkswagen and Porsche, Peugeot and Citroen, Jaguar Land Rover, Ford, BMW, FCA and Suzuki, Volvo, Hyundai-Kia, Toyota and Mazda.

The manufacturers are resisting the claims.

The cases against "sample vehicles" made by five manufacturers - Mercedes-Benz, Renault, Nissan, Ford and Peugeot and Citroen - will be heard at a three-month trial due to begin on Monday, with the other manufacturers bound by the ruling in that case.

The trial before Lady Justice Cockerill is due to begin at 10.30am on Monday at the Royal Courts of Justice in London.

Law firm Leigh Day, which represents some of the motorists in the case, said that while the main trial is due to conclude before Christmas, legal arguments will not be heard until March 2026.

A ruling is then expected next summer, with a further trial to determine any compensation scheduled for autumn 2026.

In December 2023, a judge said the legal action was "unprecedented" in scale, with a previous hearing told that it involves more than 1,500 defendants, once dealerships are taken into account.

In July last year, barrister Benjamin Williams KC told a hearing in written submissions: "Even if the claims were valued conservatively at c.£4,000 per claim, that would give an overall value of at least £6 billion to these proceedings."

Speaking ahead of the trial, Leigh Day's senior partner Martyn Day said that if the claims were proven, it would "demonstrate one of the most egregious breaches of corporate trust in modern times".

He said: "It would also mean that people across the UK have been breathing in far more harmful emissions from these vehicles than they were told about, potentially putting the health of millions at risk."

Mercedes owner Adam Kamenetzky said: "If these allegations are true, the regulators, the politicians and the public have been cheated by manufacturers who, it's claimed, are profiting from their sale of diesel cars while flouting clean air laws and measures such as Ulez, which aim to improve public health.

"This is not just a personal issue, but one of much wider public concern: air pollution is a leading cause of ill health and premature death around the world.

"I want to speak up for people who are breathing in potentially lethal levels of pollutants and suffering the health consequences, and for vehicle owners who've thought they're doing the right thing by buying apparently less polluting vehicles, when this is clearly now in question.

"I want to see justice, and if this trial helps to hold anyone who lied or cheated to account, that's my cause."

Car emissions scandal could see 1.6 million drivers handed payout as trial begins - Birmingham Live