And power. The Ariel-tuned 2.0-litre i-VTEC Honda Civic Type R engine’s outputs increase from 320bhp and 310lb ft of torque to 400bhp and 369lb ft. In a car weighing 700kg, that means a power-to-weight ratio of 571bhp per tonne – better than a Ferrari 296 GTB. Ariel has managed to extract this additional performance thanks to new intake geometry and a redesigned cooling system that features an additional radiator in the left pod. Meanwhile, the pod on the right gets a larger intercooler that increases the car’s intercooling area by 75 per cent.

Three different engine-map settings allow the driver to select just how much they want their stomach churned, while a new (optional) six-speed sequential gearbox from Quaife can bang through full-throttle upchanges and rattle back through five downshifts in less than a second. As a result, 0-62mph takes just 2.7 seconds while 0-100mph occurs in 6.5sec.

Not that every 4R will do that. Each car is built to order by one of Ariel’s highly skilled engineers and many of the goodies are extra. For example, this car’s sequential ’box (a six-speed manual is standard), four-way Öhlins dampers plus the carbon brakes and wheels and wings are optional. Therefore, rather than the £77,940 starting price, you’re looking at around £140k as tested…

Heading north on the A470, it’s initially difficult to see why the price comes in at almost four times as much as a base Atom 4 and it’s even harder to comprehend how a bona-fide Porsche RS model could come in cheaper. And yet it does – we know this because we’ve brought one along, a 718 Spyder RS, to keep some perspective on the Atom.

A last hurrah for the mid-mounted internal-combustion engine from Stuttgart, it’s one of the finest sports cars of the 21st century and the only droptop RS model in Porsche’s range. Like the Ariel, it’s unlikely to be a car you’d use every day and its lightweight fabric roof means it’s far better suited to warmer climes. Not for a second would we claim it to be as hardcore, but that’s the point. Does it deliver enough of the thrills, with far less of the drawbacks, for its £123k starting price?

To find out, we’re initially heading north into the Brecon Beacons before looping back down into the Afan forest and its twisting, undulating asphalt. It’s a route I’ve done before and know exactly what to expect, yet the Welsh weather is proving even more troublesome than usual. As we drive past Aberfan on our right, a Dickensian fog surrounds us like an army of inquisitive ghosts and we lower the pace of our two-car convoy.

The Porsche’s carbon bonnet, wheelarch vents (first seen on the 991 GT3 RS) and centre-lock wheels look the part, yet next to the Atom 4R it’s being roundly ignored. My helmet-clad head tilted slightly forward in the Ariel to deflect the wind, I see the blur of a Honda motorbike in my dinky side mirror, its L-plate-adorned silvery form quickly drawing level and the rider peering across at this strange interloper on his Monday-morning commute. I’m terrified he’s going to try to do a wheelie and end up in my lap, but mercifully an enthusiastic thumbs-up suffices and he speeds off on his way.

I draw energy from the idea that he can’t be any colder than me in my old ski jacket and waterproof trousers, yet I’m probably more comfortable. The Atom 4 and 4R are more usable than those that came before it, and while I do covet thy neighbour in the Porsche and its lovely heater, the Ariel is reasonably straightforward to drive.

Engine map 1 delivers oceans of torque combined with steering that’s unassisted and not over-sensitive. As for the gearbox, I’m having to use the clutch for upchanges and downchanges below 50mph, yet it’s not too heavy or difficult. Even the Yokohama A052 tyres are behaving themselves despite the cold conditions. And besides – I know things aren’t entirely rosy in the Porsche.

Should the inevitable happen and the rain start to fall, I’m pre-prepped in the Atom 4R and can carry on going, yet the Porsche will need to stop and have the manual folding roof put in place to avoid soaking the old-school but still nicely appointed cabin. This is a task that takes some practice.

For now, however, the rain is holding off and the A4059 beckons. It’s a fast, challenging road that lies in the shadow of Pen y Fan, yet today the snow-sprinkled peak of the highest mountain in South Wales is hiding behind a seemingly never-ending greyness that hangs over the verdant land and adds a density to the cold, clean air.

Down at road level, however, the sight lines allow us to open up the 4R and 718 Spyder RS. With the road still wet from last night’s rainfall, I take the lead in the Ariel, free from the spray of the Porsche’s fat Cup 2 tyres clawing for purchase on the near-perfect tarmac. Ariel engine dial flicked to 2, the noise is incredible but almost comedic in its delivery. From the surge of intake sound to the chuff of wastegate and the sneeze of a rhinoceros, the noise is punctuated by its unpredictability. So much so that it initially alters my driving style as I consciously provoke the throttle pedal in order to elicit another tune from the orchestra of the unusual.

About 20 metres behind me, the Porsche has its own symphony in motion. And whereas the same wide-eyed grin follows its siren song, the similarities in sound, tone and delivery are nil. A 4.0-litre naturally aspirated flat-six extracted from the 911 GT3 and manhandled into the far smaller 718 chassis, it sits in the mix like a flaming, vodka-soaked cherry atop a perfectly balanced Black Forest gateau.

The Boxster chassis is a peach, but the 493bhp engine (slightly less power here than in the rear-engined 911 GT3, as the exhaust follows a more convoluted path) is the star of the show. For sheer shock-and-awe pace, the Ariel beats it all ends up, yet in every other respect – responses, linearity and sound – the Porsche’s flat-six reigns supreme. Quite how Porsche can ever try to replicate this experience with an EV is an intriguing question, yet one that will no doubt be answered soon.

We point the cars south and leave the invisible mountains in the Ariel’s dinky side mirrors, now caked in the salt and slime of the well-worn tarmac beneath us. Like desperate lizards, we hunt down a shaft of sunlight on the horizon, flying past the Penderyn Distillery (home to some fine Welsh whisky) and caves of Ogof Fawr before making a brief detour for fuel south of Treorchy.