Nosing around Alfaholics’ workshop leads to a significant discovery. Stashed away in a corner is a car only the true cognoscenti recognise, and fewer still genuinely yearn for.

Well, it’s good to keep some secrets. It’s an Alfa Romeo Junior Z, designed by the great Ercole Spada, author of so many Sixties icons (mostly wearing Zagato badges), now enjoying a full Alfaholics restoration. “Ah,” company boss Max Banks says, a little conspiratorially, “that’s just arrived. It’s owned by Gordon Murray. He likes what we do here.”

This makes perfect sense. Max and his brother Andrew have successfully transformed their father’s 40-year old mail-order parts business into the world’s leading Alfa 105-series specialists. Successful historic racers in their own right, competition-inspired solutions soon made their way onto Max’s personal car, a vehicle which has now travelled a very long way indeed from the 1967 ‘step nose’ 1300 GT Junior it left the Alfa Romeo factory as.

Alfaholics’ primary business is still in mail-order, but when increasing numbers of clients began pestering Max for the parts he’d been developing for his car, he realised that something was up. Along with Singer’s incomparable reincarnation of the classic 911, Ikon’s reimagining of the Sixties Ford Bronco, and JLR’s classic division ‘remastering’ of its back catalogue, the Alfaholics GTA-R, a resto-mod evocation of the GTA racing car, is answering a question an increasing number of well-heeled car enthusiasts have been asking.

Actually, let’s boil it down to one word: weight. Max’s car tips the scales at a featherweight 830kg. Its engine is the classic Alfa Twin Spark 2.0-litre, bored and stroked to a 2.3-litre capacity, and now producing 240bhp and 200lb ft. This results in a power-to-weight ratio of 290bhp-per-tonne, an appropriate naming device, when you think about it. It follows that the car is physically tiny, although it’s surprisingly space efficient inside. You climb over a roll cage and wriggle into bespoke Recaros, your body clamped into place via a four-point harness. Needless to say it feels absolutely wonderful. The dials are faithful copies of Veglia and Jaeger originals. The pedals are carved out of solid aluminium by the man who did the turned aluminium on the Bugatti Veyron. You can almost smell the attention to detail.

The list of technical highlights is long, and includes carbon-fibre doors, bonnet and boot-lid, an aluminium propshaft with rifle-drilled half-shafts, counter-weighting on the pistons, gas shock absorbers that adjust for bump and rebound (a very trick solution), and six-pot aluminium front brake calipers with comically large 300mm ventilated discs.

Hinges, fasteners and screws are all ultra-lightweight. Max gives me a tour of the warehouse, and hands me doors, windows and engine parts, all of which require minimum effort to lift. Alfaholics makes most of the components itself, but the people who make the bits that it doesn’t are the best in the game. “The company that does our CNC milling is a mile away,” Max says. “It’s Airbus’s biggest subcontractor.”

The GTA-R feels every inch a wieldy little racer. There’s a competition clutch, lightweight flywheel and unassisted steering (power assistance is available, but why bother?), but it moves with the simple grace and poise that only the most finely engineered cars command. Everything stems from that 830kg weight figure: the engine doesn’t overwhelm the chassis, and even on the unpredictable twists, turns and uneven camber of the roads around Devon, it’s fabulously composed. I expect it to crash and thump. Instead, it flows and glides.

Its body control is fantastic – there isn’t all that much to control, after all – and the steering wheel is alive in your hands and dense with the sort of information modern cars have long since sacrificed on the altar of fully electric power assistance. The gearbox uses a standard linkage (with bespoke synchros and bearings), and while the shift is long, as per original 105 spec, it’s quick moving and perfectly precise. Two other notes: it’s plenty fast enough to smear a huge smile across your face, but not so fast that you need to offset your thrill-seeking against a possible prison term (0-62mph in 4.6 seconds, top speed of 145mph). And it sounds utterly magnificent, perhaps the fullest, ripest four-cylinder you’ll ever hear.

There is one major problem. In the UK, Alfaholics charges £240k for the GTA-R 290, and there’s no getting round the fact that this is a huge sum of money for a worked-over 50-year old Alfa Romeo. But what a work-over. And what a car.