A landmark trial opened at London’s High Court on Monday, as five global car manufacturers face accusations of using illegal devices to cheat emissions tests, a case that could reshape the UK’s automotive industry and cost billions in compensation.

The three-month hearing will determine whether Mercedes, Ford, Peugeot-Citroën, Renault, and Nissan installed systems designed to manipulate nitrogen oxide readings and appear cleaner than they actually were. The outcome is expected to set a legal precedent for similar claims against other automakers.

The claims, brought on behalf of 1.6 million motorists, target 14 manufacturers in total, including Jaguar Land Rover, Toyota, Vauxhall-Opel, and BMW.

Martyn Day, a lawyer at Leigh Day representing the claimants, said the case could result in “serious amounts of compensation.”

“The most important thing for us is to persuade the judge that there are defeat devices in all of these cars,” Day told reporters outside the court.

The scandal traces back to 2015, when Volkswagen admitted to fitting millions of vehicles worldwide with “defeat devices” that allowed engines to pass regulatory tests while emitting far higher pollution levels on the road. That revelation triggered global outrage and investigations into several other carmakers in Europe, the US, and Asia.

In London, the High Court will examine whether similar software was used by the five lead defendants to reduce emissions readings during testing. All five companies deny wrongdoing.

Outside the courthouse, clean air advocates and affected families gathered in protest. Among them was London resident Rosamund Adoo Kissi-Debrah, whose nine-year-old daughter, Ella, died in 2013 from an asthma attack linked to air pollution.

“The coroner said if it wasn’t for the illegal levels of air pollution where we live, not only would she not have got asthma, she wouldn’t have died on that fatal night,” she said, calling for an apology from the manufacturers.

Campaigner Jemima Hartshorn, from the group Mums for Lungs, urged authorities to “get these cars off our roads to protect our children’s health,” warning that “millions of diesel cars” are still polluting UK streets.

Adam Kamenetzky, one of the claimants, said he felt “defrauded” after buying a Mercedes SUV in 2018, believing it was more environmentally friendly. “We live in a built-up neighbourhood in London where there are children with lungs that can be harmed immeasurably by the emissions that these cars are producing,” he said.

For now, any payout remains a long way off. The current phase of the trial will determine liability before compensation proceedings can begin next year.

Mercedes and Ford have rejected the allegations as baseless, while Nissan declined to comment. Renault and Stellantis, parent company of Peugeot and Citroën, said their vehicles met all regulations in place at the time of sale.

The case follows the 2020 High Court ruling against Volkswagen, which found the company guilty of using defeat devices. Volkswagen later settled, paying £193 million ($259 million) to 91,000 British drivers. Globally, the automaker has paid more than €32 billion ($37 billion) in fines and settlements since the scandal broke.