Bespoke restomod projects are all the rage today, and this is no great surprise.

Over-familiarity will have led to a weary cynicism in many of us, but equally who among us, given the time and means, wouldn’t love to have a crack at creating our dream car?

To set out with no commercial imperative and draft a grand vision, then obsess over the details such that the end result fitted our wants and needs like a glove? It’s fantasy stuff.

What I hadn’t appreciated until recently was the kind of person you need to be to pull it off to convincing effect, even before you’ve pinned down a team of the calibre required for expert engineering and fabrication – the people who will slowly bring your vision to life.

Most of us would be better served keeping the dream confined to a beer mat and chasing after ready-to-wear options from Ariel or Ferrari.

It makes the 0.0001% of wonder-machines that do become a reality as world-class, from-the-ground-up commissions all the more tantalising. Projects like Thornley Kelham’s recent European RS.

“Hal could walk into the prep shop, look at his car from a distance of 10 feet and tell you the sill line is two millimetres out,” says Simon Thornley, co-founder of what is certainly an elite but under-the-radar British restoration company. “And he’d be right. That was the scary thing.”

Hal Walter is a retired Australian architect who spends half his time in the Alps. This partly explains why his commission took the form of a 911 restomod blending the spirit of a 1973 2.7-litre RS and the more recent 997-generation GT3 RS 4.0, which he also owns (of course he does).

It was an ambitious concept, but Walter is a man for details – every last one of them.

Shortly after Thornley Kelham agreed to take on the project, a near-40-page document arrived: the instruction manual.

When we visited the firm’s premises last year to see and drive the 95%-finished European RS, Thornley produced a printout and dropped it onto a table. It landed with a pronounced slap. “This is about the fourth version,” he said. “We’re now on version 23.”

The level of detail in this tome was exquisite, inspiring, just a little unnerving and perhaps understandable for a man with an architect’s mind and many, many hundreds of thousands of pounds on the line.