Self-styled as the Erin Brockovich of the Potteries, and described by the court of appeal as “a postman with a penchant for fast cars”, Andrew Wrench is a force to be reckoned with.

And while he may not be a household name yet, those who work in the multimillion-pound car-leasing industry will be all too aware of his campaigning zeal.

Wrench is one of a small group of motorists who could have won billions of pounds for consumers across the country by taking on two finance companies in the courts.

Wrench, 60, who lives in Trentham, Staffordshire with his wife, Louise, 46, and 16-year-old son, Ethan, has no legal training but was motivated to fight his case after he discovered that car finance lenders had been paying commission to the dealerships where he bought two cars – an Audi TT coupe and a BMW 3 Series – without his knowledge.

“They were kind of pushing their finance straight away, as they do, because that’s where they make the money on the sale of the car, the interest and everything else linked up,” Wrench said. “Lo and behold, I didn’t know about any secret commissions. Obviously, at that time, it hadn’t been disclosed.”

In 2015, he bought the Audi for his wife for £8,995, paying a deposit of £3,000 and financing £5,995 on a 48-month credit agreement. “It was a car that my partner, Louise, had always wanted,” Wrench said.

He bought the BMW in 2017 for £9,750, paying a deposit of £1,000 with the balance of £8,750 also financed over 48 months.

It was only later, when he went back to work after retiring for a period to look after his parents, that he began to question how much he was repaying on the loans.

“I took four years out of work, and the APR was lower, when I returned to work in 2019 the interest rate was higher by 5% and I thought, ‘Oh, that’s strange’,” he said. “So I started reading in depth the paperwork, and came across this clause about commissions.”

Wrench, a former miner who also served in the navy, sought legal advice and instructed a Bradford-based firm, Cooper Hall Solicitors.

After a months-long legal battle against the billion-dollar FirstRand bank, which started in the county court in Stoke-on-Trent, at the end of last month three judges at the court of appeal ruled in favour of Wrench and two other claimants who had brought similar cases.

Earlier this year, the Financial Conduct Authority (FCA) launched its own investigation into car financing, seeking to determine whether customers had been charged too much interest on loans, with an update due in May next year.

The money-saving expert Martin Lewis said in his newsletter that “a shock [had] exploded through the car finance world” with the judges’ ruling.

“That means this is now the law, though if it goes to a supreme court appeal, that could take a different view and overrule it,” Lewis said. “The verdict was unambiguous and said a car sales firm couldn’t lawfully receive commission from a finance firm unless it had the customer’s ‘fully informed consent’.”

The landmark case may result in finance companies paying out billions in compensation to borrowers.

“I’m a very, very determined person,” Wrench said, explaining why he decided to take on two finance companies. “I’m very honest, I have a great deal of integrity, to never let go if I think something’s right.”

He added: “It’s made me feel good about it, how I’ve done it, and all those people coming forward to open up some sort of small claim. They’re probably doing it in principle, not for the money, but it is nice to know that they’re going to get their justified rewards.”

“I always relate to Erin Brockovich,” Wrench said. “That film captivates you. It shows you. They had a massive law firm … and then the water treatment plant ended up dishing out millions to those genuine people. I think it’s similar.”

Jamal Ahmed from Cooper Hall said: “After a lengthy legal battle and the involvement of consumer rights solicitors, we are very pleased with the court of appeal’s decision.

“This outcome validates our efforts and underscores the importance of transparency and fairness in financial transactions. It also highlights the necessity of holding financial institutions accountable for their practices.

“This ruling is a significant win for consumers across the UK. It sets an important precedent, reinforcing the need for full disclosure in financial agreements to ensure that individuals are informed about any commissions that may influence the terms of their contracts.

“We believe this decision will encourage more equitable practices within the car finance industry and empower consumers to make better-informed decisions”