When we think of classic cars, we think of sleek Jaguars and pretty Alfa Romeos clattering their way to a car show. But because time now flies faster than Concorde, we've completely missed the fact that SUVs are now classics too. The car that defines the genre - the original Range Rover - is now 50 years old, and that makes it a desirable classic in its own right.

Of course, it was desirable anyway. It has that timeless design that was in production for more than 20 years with barely a modification, the mix of luxury and practicality that makes high-end SUVs desirable to this day, and there's Land Rover's legendary off-road capability. The Range Rover really does have it all.

Including Land Rover's infamous reliability record. British Leyland couldn't make a car that worked 10 minutes after it left the factory, so expecting it to work around half a century later feels optimistic in the extreme. Susceptible to the metal moths, overheating and more leaks than the Titanic, owning a classic Range Rover is something of a leap of faith.

But I really want one...

This is where Kingsley comes in. The British company takes solid but tired Range Rovers and turns them into cars you could quite happily use every day. Or at least almost every day. Think of it as a halfway house between a faithful restoration and full-on restomods.

This idea of turning classics into working cars is nothing new. Eagle has done similar work to the E-Type for years, and in a damning indictment of Land Rover's engineering, Twisted has been busy turning old-shape Defenders into working SUVs. And it was doing so even when they were fresh off the production line.

Like those companies, Kingsley takes all the Range Rover's weak spots - which means pretty much everything - and fixes or improves them. The bodywork and chassis are both fixed up and rustproofed, the engine is swapped for a modern 4.0- or 4.6-litre V8 petrol engine, depending on your specification, and the gearbox is a modern eight-speed automatic. Oh, and the interior gets a makeover, too, including the addition of a touchscreen infotainment system and the Apple CarPlay smartphone integration software.

So it's a modern car with classic styling?

Not quite, but it certainly feels that way. Kingsley sources the car for you, then strips it down completely, sorting out the paintwork, rustproofing the chassis and undersealing everything. That keeps the rot at bay, as long as the car is returned to Kingsley for retreatment every five years. That done, the company swaps in a modern V8, a modern gearbox and uprated brakes, plus some improved suspension.

On top of that, there's the retrimmed interior and all the electronic goodies such as the wireless phone charging, parking sensors and reversing camera, although that depends on what the customer specifies.

But that's about it; plenty of parts are shared with the original. For example, Kingsley leaves the original olde-worlde analogue dials and the heating and ventilation system, largely because the wiring loom is unchanged and modern climate control would overload the electrics.

And although there's a central locking system that definitely isn't period, this is still an original three-door Range Rover, complete with a milled key that you insert into a slot beside the steering wheel and turn to start the engine. It's old-school compared with the push-button ignition we find in modern Range Rovers, but it works.

That makes a change...

Exactly. That's what the Kingsley is really all about. The PR people bang on about the Ultra-Low Emission Zone (ULEZ) in London - and that's where we went for our test drive - but this is really just a way of making an understated and stylish classic car work properly. The usual Land Rover issues of overheating and rust are supposedly banished, leaving us with a classic 4x4 you could use every day.

Of course, whether you would want to subject a three-door Range Rover that costs well over £125,000 to the school run, salted roads and perilous supermarket car parks is another question, but it's nice to know you could. In theory, at least, the Kingsley treatment makes the Range Rover even more reliable than it was when it left the factory. Although that isn't saying all that much.

So what's it like?

Pretty awesome, really. The car we tried was a 1971 three-door originally built for the French market. With a steering wheel on the wrong side of the car and a 4.6-litre V8 producing around 270hp, it didn't seem ideally suited to tackling London's congested, palpitating heart.

How wrong could we be? Slipping inside revealed a world of soft leather and tweed trim, which gave it a timeless, old-money vibe. Swapping a brand-new Range Rover's digital dials and multi-zone climate control for the Kingsley's more rudimental equipment never feels like a hardship. It's just quite charming. But it still comes with some nods to the modern world, including Apple CarPlay, which meant we could dodge the traffic on the Strand and get fair warning of the roadworks on Embankment.

And it's absolutely glorious to drive. The V8 doesn't have the punch of a modern Range Rover's supercharged 5.0-litre - it's lazy and indulgent and it slouches into action - but it has character in spades. There's a muscle car kind of charm to its power delivery, and the grumpy growl it emits when you coax it into life is endlessly endearing. As is the rough grumble that bubbles from the pipes at idle.

The steering is heavy, but it's responsive and direct, which gives you plenty of feel for those massive tyres. That said, it never feels jerky or fidgety when you're going over bumps in the road. It's pretty much perfect, and the same has to be said of the suspension. Of course, such a big old car will lean through corners, but the Kingsley rides out imperfections in the road with consummate ease. Massive tyres and long-travel suspension help, but this classic 4x4 rides better than some of its modern equivalents.

And although we didn't get to try this on our slow-paced London test route, Kingsley claims the car will be just as competent off-road as it was when it was new. You could, if you wanted, take this overlanding. It seems churlish to treat such a beautiful thing that way, but it's nice to know you can.

Other advantages to the Kingsley include the visibility, which is aided by narrow roof pillars and plenty of glass, plus the compact dimensions. Despite being a Range Rover, it's narrower than a modern Nissan Qashqai.

It's also surprisingly well loved. Even in London, a city where the V8 is a symbol of emissions and conspicuous consumption, the Kingsley was revered. Cabbies wound their windows down to tell us how beautiful the car was, while pedestrians turned and stared. Other drivers waved us through at junctions and let us pull across into another lane. It just wouldn't happen in a modern Range Rover.

Sounds fab. How do I get one?

Ah. Kingsley says prices start at £125,000, but this is essentially a bespoke car, and you can easily spend far more getting it exactly how you want it.

If you love the look of a Range Rover Classic but don't fancy tackling the myriad associated issues, this will be the ideal car for you. But with that huge price tag, it's difficult to see this car being used as much more than a toy. That's a shame, really, because it's much cooler than the latest Range Rover, and almost as easy to live with.