Currently reading: How Ellesmere Port was saved: inside the old Astra factory's revival

Diane Miller's remarkable leadership has helped transform Stellantis' massive UK plant

Diane Miller, Stellantis’s top UK car manufacturing executive and winner of Autocar’s 2025 Editors’ Award, has loved cars all her adult life – preferably in very large numbers – and can vividly remember the day the obsession began.

From a post-graduate job at Ford’s then mighty Ford Fiesta plant in Dagenham, Essex, Miller has spent the past 30-odd years mastering ever more responsible automotive jobs around the world – for Ford, Aston Martin, GM and most recently Stellantis, in the UK, Europe and the US.

Miller is decisive but modest and as a result reluctant to identify any particular secret of success. But if you converse with her long enough, she will eventually admit to one asset: “Finding a way to get on with people.”

It is for this that she is known and loved by the people who have worked for her. Having discovered its effectiveness early on, she has deployed her liking for people in every car job she has had, and she has become famous for it.

Miller’s most spectacular achievement to date has been the 18-month conversion of the former Vauxhall Astra plant at Ellesmere Port, near Liverpool, to the manufacture of battery-powered delivery vans for five Stellantis marques: Vauxhall, Opel, Citroën, Peugeot and Fiat.

It has been a vital move in rescuing volume vehicle manufacturing in this country. Now that this EV factory conversion has been achieved, Miller is turning her hand to running Stellantis’s massive new national parts distribution centre, located just down the road from the van plant at Ellesmere, where the company is spending £500 million to expand and improve the way it delivers components to its customers in the UK and Ireland.

The parts centre project has required another wholesale reorganisation, entailing both the redeployment of car-making people and the importation of new workers into a business that, despite its size and scale, has to be very labour-intensive.

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It is a perfect place for a unique character like Miller, a highly experienced engineer who discovered early how to get on with people.

“I went to an all-girls convent grammar school in Northern Ireland,” she explains, “and three of us opted for A-level physics. Our teacher loved engineering, and the upshot was all three of us chose engineering at university: mechanical and production engineering for me; civil and aeronautical for the others.

“My degree was from Liverpool John Moores University, and as part of a ‘jobs milk-round’ for graduates I was invited to Ford’s Dagenham plant to see how it was run.

I was instantly amazed and intrigued that they could build 60 cars an hour, and the experience had a lasting effect on me. Even after more than 30 years in the business, I still find it amazing.”

Miller joined Ford, moved to Dagenham and stayed five years. She achieved rapid promotions, first to senior process engineer and then to a manager’s job in the paint engineering area, launching new technology in Ford plants across Europe.

Paint doesn’t suit everyone, but Miller earned an early reputation for being willing to try anything and work anywhere.

“Crossing the Irish Sea to go to university was the big move,” she says. “After that, anything was okay.”

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Pretty soon Miller was heading to Chicago on a two-year paint unit training scheme that extended to four. “It was a situation that occurs in many companies,” she says. “You go on a training scheme and the money runs out, so they get you to do the job anyway. It was great training because no one else knew about paint, so I had to make the decisions. It worked out okay.”

Miller’s career progressed more rapidly than most young engineers her age, but she’s careful not to give herself much credit. “I had very good mentors,” she says. “And there were so few women in the industry in those days that people probably noticed you more. Mind you, even today I’m very sad that there aren’t more women in these engineering jobs. There are great careers here for those who want to try it.”

Women can succeed in a male-dominated arena like car-making just by being who they are, says Miller. They tend to humanise the place, she says: “Right from the start, I’d go to a factory, talk to the operators and ask how their job should be done. It was a bit different from some managers who arrive and think, well, ‘I’ve got the degree, so I know how things should be run’. But people on the floor can work smart better than anyone, and if they trust you, they’ll tell you how.”

When the Chicago gig ended, Ford wanted Miller to go back into central engineering at Dagenham, but she wanted to stay in a plant and felt that would have been a waste of her paint know-how. So she worked happily for several years at the Ford Transit plant in Southampton, leaving before it closed in 2013 because its manager was heading for Aston Martin (then a Ford company) and asked her to join him, bringing her paint expertise.

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It made sense, because her husband, an American, was already a paint supplier there. Aston Martin paint is quite different from Ford Transit paint, she found: “I started off thinking five jobs an hour would be easier than 60 jobs an hour, but that was completely wrong. True, Aston paint was very different – many more coats and lots of polishing – but the big difference was the fact that the operators had so much to remember.

The Transit takt (process) time was around five minutes, explains Miller, whereas at Aston it was more like 25 minutes. People had to remember 25 minutes’ work rather thanfive, which is clearly much more difficult.

Still, Miller thrived there for six years – until Ford sold Aston Martin and suggested, once again, that she return to central engineering. Just in time a GM headhunter arrived with an offer to move to Ellesmere Port where Vauxhall was about to launch the Astra D2, but there were big problems with the paint shop.

Miller, uniquely qualified to take hold of the process and fix it, was perfect for the job. Aston was small by comparison, and Miller liked the Liverpool area where she had been at university.

“We decided to make the move, and I joined the company at a high enough level to make the changes needed,” she says. “Our Astra launch was the best in the company’s history, and I thoroughly enjoyed it. From that I was asked to take over general assembly, another progression. I had enjoyed paint, but there are many more people in general assembly, and I guess that’s where my skills are. We made some good progress; people felt able to tell me about their difficulties.

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They knew if there was a problem and I could fix it, I’d do it right away.” Astra production ended in April 2022 – with quality levels higher than they had ever been. Then came the bombshell decision to start making Stellantis electric vans. “It was a funny time,” says Miller.

“The whole of Europe thought this plant would never reopen, but we already knew [then Stellantis boss] Mr Tavares had decided to keep it going because he’d discovered – from the first time he visited us – that there was an ethos among Ellesmere people that we’d find a way to do whatever was needed to keep the place open.

In order to make the changes, the factory was shut for 18 months. Staff who couldn’t make cars helped move robots and build new rest areas. Managers went to Madrid, where changes planned for Ellesmere had already been made, to see exactly what was needed. Everyone adapted, in no small part because Miller’s can-do culture had spread throughout the place.

By September 2023 electric vans were flowing down the lines. The success isn’t complete. For Miller and Stellantis, the current 20,000-unit annual output isn’t nearly enough, mostly because they believe the government’s re-adoption of 2035 as an ICE cut-off date has hurt demand for Ellesmere’s all-EV output. As a stopgap, they have begun building bodies for an ICE van plant in Algeria (boosting output to 50,000 units), and production will soon be further augmented by the arrival of a range of larger, Vivaro-sized electric vans for the five Stellantis marques.

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Ultimately, demand will be much higher – perhaps as high as the plant’s 100,000-a-year, seven-day, three-shift capacity. Ellesmere Port is ready. Miller, meanwhile, is several months into her demanding new project – and she will be happy with more after that.

She has spent most of her three-plus decades in automotive providing a great role model for other people, not just women, but she says the lessons she has learned have been important in her own personal development, too. “I’ll never forget how those early days at Dagenham flipped my mind,” she says.

“They taught me that if you think clearly, you can do anything. I started applying those principles to my own life and found that there’s nearly always a way you can make things happen. This industry has been a great teacher.”

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Steve Cropley

Steve Cropley Autocar
Title: Editor-in-chief

Steve Cropley is the oldest of Autocar’s editorial team, or the most experienced if you want to be polite about it. He joined over 30 years ago, and has driven many cars and interviewed many people in half a century in the business. 

Cropley, who regards himself as the magazine’s “long stop”, has seen many changes since Autocar was a print-only affair, but claims that in such a fast moving environment he has little appetite for looking back. 

He has been surprised and delighted by the generous reception afforded the My Week In Cars podcast he makes with long suffering colleague Matt Prior, and calls it the most enjoyable part of his working week.

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