“From a neighbouring family—absolutely stunned,” read one bouquet. “You were all such a lovely family,” read another.

According to his friends, Foster adored his family in a very ordinary way. He was apparently forever seen laughing and joking and cuddling them while watching TV and so on, right up until the night he murdered them.

I read the condolence cards for a few minutes and then a policeman pulls up.

“Can I help you?” he asks.

I show him my press card.

“You look too scruffy to be a journalist,” he says.

We both laugh. Then I bid him farewell and drive away. Now the police are following me, past the gated mansion belonging to John Hughes, the millionaire luxury car dealer whose barbecue and clay-pigeon shoot the Fosters attended a few hours before the murders; past their local pub, the Black Horse Inn; and toward my meeting with Foster’s friend and blacksmith, Ian.

Had this been a working-class double murder-suicide, I don’t think the police would have bothered following me all the way out of town, but Maesbrook is a rarefied, aspirational village, and they seem to want to make absolutely sure I’ve gone.

Once I’m out of the village limits, the police car turns around and I make the final part of the journey alone. Ian lives in Meifod, Powys. He’s a friendly, welcoming, shaven-headed man with five horses and eleven acres. We sit in his kitchen. He makes me a cup of tea and says he keeps remembering a weird incident that occurred a month before the murders.

“Before I explain what it was,” Ian says, “let me tell you something about Chris Foster. He was always busy, messing with the horse trailer, cleaning it, fixing this or that, taking out trees. He was always home. I did wonder why he wasn’t at work. I knew he was something to do with oil, and everyone called him ‘the Millionaire,’ but he was always home. He kept his barn spotless.”

“That’s weird,” I say, in a dark chuckle, “to keep a barn spotless.”

“I keep mine spotless too,” Ian says.

“Oh, well, not weird . . .” I say.

“Let me show you my barn,” Ian says. “And then I’ll tell you about the weird thing that happened a month before the fire.”

On the way to the barn I tell him what I’ve learned about why Foster was always home. In 1997, he had a eureka moment. He invented, and patented, a new chemical formula.

“It came to him in a flash,” said Terence Baines, who’d been his accountant back then. I had phoned Terence shortly before leaving for Shropshire. “Before then, he was just an ordinary bloke from Wolverhampton,” Terence said, “a salesman living in Telford, working for some company that went bust. But one day he suddenly thought, ‘Hang on. If I get a bit of this and a bit of that, a bit of special rubber and plastic, and put it all together, it’ll make a new type of oil-rig insulation.’”

Foster called his invention Ulva Shield. It won an apparently fantastically rare A1 fire-test rating. Where other oil-rig insulations burst into flames, Ulva Shield just formed a safe, crisp shell. The big oil companies began placing orders.

“The company went great guns,” Terence continued. “Chris started dressing very smartly. He wanted to present himself well. He liked good holidays, a decent car . . .”

Actually, he bought a fleet of decent cars—two Porsches, an Aston Martin, a 4×4 for his wife (with the license plate JILL 40), and a tractor for the mansion, Osbaston House, that he’d bought in Maesbrook. He was doing an extreme version of what an awful lot of people were doing back then: living on credit, believing the boom would never bust. “He never planned on what things would be like when he was sixty-five or seventy,” Terence said. “It was always ‘What can I do now?’”

Along with the mansion and the cars, there were the affairs. Foster had at least eight mistresses, according to Jill’s sister, Anne Giddings. “He had a big thing about blondes,” Giddings later told the Sunday People. “Jill knew all about his affairs. There were lots of women on the scene. But she played the dutiful wife and kept quiet. He wasn’t a good-looking guy, but money did the talking. He was always flashing the cash—it seemed to give him confidence.”

But then it all went bust. In 2003 Foster contracted a supplier, DRC Distribution, to manufacture Ulva Shield exclusively. But by 2005 his liabilities were £2.8 million higher than his assets, presumably because he’d spent so much on mansions and Porsches and guns and membership to various fancy clay-pigeon-shooting clubs. In desperation, Foster sourced a California supplier who could manufacture Ulva Shield cheaper. DRC found itself lumbered with a warehouse full of Ulva Shield it couldn’t sell because it was patented to Foster. DRC sued and won.

At the Royal Courts of Justice, on February 28, 2008, Lord Justice Rimer said Foster was “bereft of the basic instincts of commercial morality. He was not to be trusted.” And so it all came crashing down. DRC took control of the Ulva Shield patent. Foster may have been lacking in commercial morality, but he certainly knew how to invent a good new fireproof chemical formula. Under DRC’s less flashy stewardship, Ulva Shield has become a huge deal in the oil-rig world, supplying to Exxon, BP, Shell, and thirty-nine other giants. Foster, meanwhile, suddenly found he had nothing to do but stay home and look after the horses and the fifteen acres.

We reach Ian’s barn. It really is spotless. The hay is as smooth as a freshly made bed at a posh hotel. “Our horses are our lives. They’re everything to me and the children. I’m going through a divorce at the moment—”

“Anyway,” I interrupt, “something weird happened a month before the murders . . . ?”

“Oh yes,” Ian says. “I was at Osbaston House when there was an almighty crash. A massive branch, as big as a tree, had come off a willow and crashed onto the path. Chris came running up. He said his tractor had been parked exactly where the branch had landed, but he’d decided for absolutely no reason to reverse it forty yards out of the way a few minutes earlier. It was a lucky escape.” Ian falls silent. Then he adds, “Although if it had hit him, it would have been a godsend for the other two.”

“Is that the weird incident?” I ask.

“Yes,” Ian says.

“It doesn’t seem that weird,” I say.

“Well, think about it,” Ian says.

Ian says it didn’t strike him as weird, either, at first, “but after the murders I was just so gutted, I started obsessively watching the news. . . . There was something about going to that place that was so nice. It was the welcome you had, from both of them, but especially Jill. She was bubbly, always had that same smile, always turned out very well, but not flash, just very well-groomed. Kirstie was very quiet but polite. And Chris would always give you a big handshake.” Ian pauses. “So I was watching the news, and I saw those pictures of the burned-out tractor, and it hit me. Chris had had absolutely no reason whatsoever to move the tractor that day. He said it himself. He didn’t chalk it up to anything. He just moved it. This was a man who invented a product. You have to be pretty active in your brain to invent something. And now he had so little in his life that he needed to fill his days by just moving a tractor up and down a path for no reason.”

We head inside. Ian makes me another cup of tea. We sit in silence. Then Ian says, “What Chris did has put thoughts in my own head, I must admit.”

“Sorry?” I ask.

“I empathize with Chris,” Ian says. “And I feel guilty for empathizing.”

“What do you mean?” I ask.

“Don’t get me wrong,” Ian says. “There’s no way I could harm my children. But I’m going through a divorce at the moment. It’s looming. I probably seem normal and relaxed to you, but inside I’m finding it very stressful. My chest is real tight. I get this pain down here.” Ian points to his left side.