In a defining moment for the global auto industry, five major carmakers — Mercedes, Ford, Renault, Nissan, and Peugeot-Citroën — have gone on trial in London, accused of manipulating diesel emissions tests to make their vehicles appear cleaner than they really were.
The case, now before the High Court, is being described as the largest group action in English legal history, with more than 1.6 million UK car owners seeking justice. The trial could last three months and potentially cost the manufacturers over £6 billion in damages, setting a precedent that may ripple across the automotive world.
At the heart of the case are allegations that these brands installed illegal “defeat devices” — software designed to detect when a car was undergoing official emissions testing. During tests, the system would temporarily cut nitrogen oxide (NOx) emissions to meet legal standards. But once back on public roads, those same cars reportedly emitted far higher levels of pollution.
Lawyers representing car owners accuse the companies of choosing profit over responsibility, arguing that automakers could have easily complied with the law through simple design changes — like fitting larger AdBlue tanks or requiring more frequent refills. Instead, they say, manufacturers opted to keep customers happy and sales high by “cheating to sell cars.”
This new trial brings the world back to the shadow of “Dieselgate,” the 2015 scandal that first erupted when Volkswagen admitted to using similar defeat devices in 11 million cars globally. That revelation led to more than €30 billion in fines and settlements, and the shockwaves are still being felt across the industry.
During opening statements, lawyer Thomas de la Mare KC said the industry’s actions had a human cost. Citing a study from the Centre for Research on Energy and Clean Air, he noted that excess NOx emissions contributed to an estimated 124,000 premature deaths in Europe and the UK between 2009 and 2024. “Each player in the industry,” he told the court, “made a conscious decision that customer convenience was more important than preventing pollution that causes death.”
The automakers, for their part, strongly deny any wrongdoing. Renault called the case “riddled with errors,” Ford’s lawyers labeled it “scientifically illiterate,” Mercedes argued that it oversimplifies diesel engineering, and Nissan said it rests on an “untenably broad” legal interpretation.
Outside the courtroom, campaigners for clean air gathered to mark what they called a long-awaited moment of truth. Among them was Rosamund Adoo-Kissi-Debrah, whose daughter Ella became the first person in the UK to have air pollution listed as a cause of death. “Illegal pollution from diesel vehicles has caused thousands of premature deaths,” she said. “This is a day of reckoning.”
The trial’s first phase — focused on evidence and cross-examination — is expected to run until Christmas, with legal arguments continuing into early 2026. A final ruling is expected next summer, possibly followed by a separate compensation trial.
If the court rules in favor of the claimants, it could mark a historic moment of accountability for the global auto industry — one that forces carmakers to confront not just the cost of cheating, but the real-world consequences of their choices on people and the planet.
