Haynes International Motor Museum set to re-open as sophisticated £5m visitor attraction

“This is my sad story,” Haynes' wife of 50 years, Annette, jokes during the chicken course (it turns out that she's a big car nut, too, and owns a Jaguar E-Type among others). “I sit here and think of all the exotic holidays I could have had. Instead of which he goes out and spends it all on cars.”

Haynes, as generations of aspiring mechanics will know, is the man who taught the world how to change its oil and check its spark plugs. Since his first service and repair manuals appeared almost 50 years ago, with their characteristic illustrations of stripped-down motors, he has sold more than 200 million copies in 15 languages.

Now, as his oldest son, John “J” Haynes, 46, steers a company with annual revenues of £30m into a challenging new era of YouTube how-to videos and DIY-unfriendly cars, Haynes senior, 76, is enjoying the fruits of his labour. An old Morris Oxford was his first vintage acquisition but several cars were soon scattered across the Somerset-Dorset border, where the family business is based. In 1985, he stuck 33 of them in a disused sawmill in Sparkford near Yeovil and called it a museum.

Next week, the Haynes family will gather again for a rather grander occasion than today's lunch at the re-launch of the Haynes International Motor Museum. Marc Haynes, John and Annette's second son, has led a £5m project to turn a series of large sheds into a sophisticated attraction designed to draw ever more visitors from the nearby A303 holiday route to the south-west.

His ice cream soon demolished, Haynes senior heads into the museum, which has remained open during the extensive works, to show off his favourite car. It gleams on a pedestal: a 1931 Duesenberg model J Derham Tourster. “It's a long time since I've done this,” he says as he hauls himself behind the wheel to be photographed. “You've heard the expression, it's a doozy? Well, this is where it comes from. Isn't she beautiful?”

The Doozy, a yellow version of which represented the elegant excess of its era in the recent film adaptation of the Great Gatsby, is one of only seven of its type to exist, and Haynes values it now at almost £6m. It sits among other classic American cars, including a Mustang that the family used in Los Angeles while setting up business in the US in the 1970s (the US still accounts for 75 per cent of manual sales). Its engine no longer roars, but the car, like many here, still hums with memories.

John Haynes sits on the wheel of the 1996 Ferrari model driven by Michael Schumacher. His son Marc (left) also raced cars in the Porsche Club (Russell Sach)
Marc, who remembers a trip in the Mustang to Disneyland, is at his most nostalgic when he positions his wheelchair alongside his old Porsche 911 and a Ferrari 360. As Britain's first paraplegic car racer (he has never had full use of his legs) he used to compete in them using hand controls alongside able-bodied drivers.

The most evocative car for Haynes senior is an old Austin 7 near the entrance. He spent his early childhood in Ceylon, now Sri Lanka, where his family had a tea plantation. As a baby, he would “drive” with his plate while sitting in a highchair. Later, at a Kent boarding school in the 1950s, Haynes followed a trend for converting Austin 7s into stripped-down racers. Still in his teens, he used artistic and entrepreneurial talents to produce 250 booklets about the process to sell via a classified ad in a motoring magazine. “Damn me if they didn't sell out in about 10 days,” he says. “I knew I was on to something.”

The manuals business has survived several bumps in the road, diversifying recently to include guides to space stations and even babies. None of the family accepts that the need for them is dying, even when sales are challenging. “Electronically, things can be a bit difficult now but you've still got clutches to change and disc pads to renew,” Haynes senior says. His youngest son, Chris, 41, says that only the notion of tinkering has changed. “Back in the day, a man knew what a four-stroke engine was, now it's RAM and gigabytes and that kind of stuff,” he explains. “Things evolve.”

They do, too, in the museum, where Haynes' sons are encouraging him to buy fewer cars. They range now from a replica 1885 Benz Motorwagen – the first car of all – to a contemporary fleet of classics in the making. “It doesn't feel like going to a museum when I come here,” he says before driving away in his Lexus sports car. “I walk in and it feels like an extension of my home.”