I don’t have accurate statistics because none will exist, but bear with. I think anecdotally it’s acknowledged that more than a few pilots subsequently become Caterham drivers, and/or that flying is something many Caterham owners turn to.

There’s something that unites the activities: mechanical interaction, guiding something analogue, feeling the elements, managing mild perils. The Seven club magazine is even called Lowflying.

Where better, then, to take a new Caterham than to what has sort of become the glamorous home of low flying in the UK: a set of valleys in Wales colloquially known as the Mach Loop, named after the nearby town of Machynlleth, where British military flyers and their friends practise screeching between the hills.

If this sounds to you like an excuse for machine-mad photographer Jack Harrison and me to stand on a windswept mountainside in the hope of seeing an F-22 scream just a few hundred feet past us then, well… rumbled, I suppose.

But what better Caterham to get there in than this one? It’s a CSR, which was a new dawn for the Kent firm when it first appeared 20 years ago. Wider than a standard Seven, it was a bigger, smoother-riding, more capable and plusher Seven, with a marginally more comfortable interior.

Faster and yet at the same time more relaxed. Better for zooming through the valleys than the harsher-riding Caterhams of old.

I can’t remember the last time I saw one. And if you’re a Caterham fetishist like me, you’ll know one if you see it. A standard Caterham Seven, by which I mean one from the regular range (not the kei car-compliant 170), is 3180mm long by 1470mm wide.

You can optionally ‘large-chassis’ a regular Seven for more room, which takes it out to the size of this CSR, 3360mm long by 1700mm wide, but the CSR has details that make it look different again.

It’s Caterham-esque but somehow not quite so. It has more aerodynamic (these things are relative) front wings and there are more holes in it to let air in and out. And where are the front springs?

They’re inboard, driven by pushrods, and next to those wings (carbonfibre on this test car) are aerodynamically profiled front wishbones.Trying to enhance the aero of a Seven is like fitting secondary glazing to one part of Blenheim Palace and hoping it will reduce the heating bills, but I suppose it all helps a little.

There’s more. At the back, although you can’t see it, it has fully independent double-wishbone suspension rather than the trad Seven’s de Dion rear end. The advantage this suspension gives ride quality is marked, and it helps improve grip and traction too. Not that even this will be able to do much about Wales in winter, given the CSR is on Toyo Proxes R888R tyres – hardly renowned for their performance in such conditions.

Ultimately, though – and this is why you so rarely spot a CSR – British Caterham buyers preferred their Sevens in the more traditional and basic ‘Series 3’ form, without the posher insides and funky outsides.

The CSR has continued to be available in mainland Europe because it passes regulations other Sevens never could, but has long since been dropped from the range here.

Until now, just as its time is up. The CSR is going off sale completely and, to mark the demise, Caterham is building a 20-off CSR Twenty edition, for sale in the UK only.

When the CSR first arrived, power came from a 260bhp 2.3-litre Ford engine breathed on by Cosworth. Owing to more limited engine availability today, it houses a 210bhp and 150lb ft 2.0-litre Ford Duratec unit, which drives through a five-speed Mazda MX-5 gearbox.

A limited-slip differential is optional but not fitted to our test car because it tends to whine a bit, and because Caterham sees this as a (slightly) more rounded proposition, it went with the quieter option. The CSR comes factory-built only, by the way – with no self-build alternative.

The CSR was always one of the more expensive Sevens but these final-edition CSRs cost – wait for it – from £79,995, more than twice the CSR’s price when it was first launched.

I do wonder if this is Caterham testing the water of what it can do with the range. Over the past few years, it hasn’t been a given that the company makes profits and, with a 170 available from £29,490 (self-build), perhaps Caterham has been thinking some models are too affordable.

Plus this is a bit of history. Caterham makes noises about the plushness of the CSR Twenty’s interior – it has some new materials, more artfully applied, but like the aerodynamics these things are relative. It is still a Seven interior, which means snug and basic.

The seats are pleasingly softly finished, there are carpets and the centre console has a cushiony soft leather finish, with Alcantara highlights around and a numbered plaque. There’s a satin-finish carbon dashboard too.

I find it easy to get comfortable in any Seven but this big-bodied version exists to accommodate the larger driver. If you’re tall or wide, it’s the variant for you. In fact, there’s so much room in the pedal box that with my size-eight feet and small trainers, the pedals are too far apart for easy heel-and-toeing.

The steering wheel is a non-adjustable leather Momo thing, the gearshift throw is perhaps the shortest in production, and the simple dials and toggle switches are pifflingly easy to acquaint yourself with. There’s a heater and a 12V socket, and even though the suspension design takes up more room than older systems, there’s still a boot, mohair-lined. Plus a roof.

I don’t imagine anybody will think that the hood itself is plush. Magazines were complaining about the popper fastenings when I was a kid and the Seven still uses them now.

Today, a Seven’s hood pulls tighter than ones of old and keeps you mercifully dry too, but it’s a bind to put up and down. Note also that the mirrors are attached to the doors and you can’t adjust them when you’re inside the car. Four-point harnesses are standard, with all the safety but faffing they entail.

Still, there’s a heated windscreen to keep misting at bay and you can reach all of the other windows with a cloth to demist those, so it’s not an unpleasant drive from Caterham’s lovely new factory at Dartford towards my overnight halt in mid-west England, even on a rainy winter’s evening.

But because you sit so low, you’ll swear that anything taller than a Nissan Qashqai has its main beams on, given how dazzling headlights are in the mirrors. By the time I reach my overnight base, I’ve decided I’d fit tinted film over them if the car were mine.

The morning is bright and, because days like this are my favourite reason to get out of bed, so is my mood. There’s no guarantee of seeing aircraft in the Mach Loop. You just turn up at a lay-by on the A487, walk up a hill, and hope.

I don’t mind either way. The drive over is pretty much all good back roads. This CSR’s 2.0-litre engine tune is the same as the 420 model’s and is a combo that hasn’t been offered in the CSR chassis before. Continental CSRs were previously running with the 485 model’s higher-revving 225bhp engine.

But if you think that having only 210bhp (at 7600rpm) or 150lb ft (at 6300rpm) is a downgrade, remember this is a car that still weighs only 620kg and it has one of the slickest, sharpest manual gearshifts in production.

Those power and torque figures arrive at high revs, so you need to work the gears, whereupon it’s amazingly urgent. At low revs it’s still responsive and linear, but at one point I leave it in fourth to overtake a truck and a few seconds later realise I should have picked third.

But even with a clear sky (and the roof down), the road isn’t going to dry today and, in these conditions, it doesn’t pay to be too liberal with the throttle because the Seven can and will break traction.

We were extremely complimentary about the ride of the CSR when it first arrived in the mid-2000s and age hasn’t wearied it. It rolls with an absorbance denied other Sevens, though I think the gap is closer than it used to be.

The compliance doesn’t bring with it a paucity of body control. The CSR is bigger than a regular Seven but the sprung masses are still light, so easily controlled. And while it’s bigger and arguably less pure than the smaller Sevens, the Caterham character is still very much intact. If you’d never driven a Seven, you’d be blown away by the lightness and immediacy of a CSR.

How much does an F-15 weigh? The internet says 14,300kg, quite a lot more than a Seven, though it seems to impact its manoeuvrability and speed very little. Jack and I haven’t even finished climbing the muddy, slippery slope when one enters from left of stage.

So close, barely higher than us, vortices trailing from the wingtips. In a moment it has passed, heading down towards Llyn Mwyngil (Tal-y-llyn Lake), before spearing left and out of view.

A road almost follows the route out of the valley, so after watching for a while (a prop-driven Texan T1 trainer and a Phenom T1 jet pass: we are having a good day), we decide to take it too. Small trainers on, teacup stowed in walking boots, I’m no more than half a mile down the road when an A400M cargo plane appears directly overhead, seen before heard, and arcs its way gently into the distance.

I’m not pretending a Seven is anything like real low flying. But as a cosplay alternative, for kidding yourself there’s an affinity, these are the roads, and this is the car, to do it.