It's a petrolhead's dream: wrestling a rusty old padlock and prising open a creaky door to unearth a classic car ripe for a loving restoration. It's called a barn find, and there are YouTube channels dedicated to this most tantalising of treasure hunts.

But what if all the legwork has been done for you? A visit to Alvis in Kenilworth can amount to precisely that.

This is a firm deep in Britain's old car-making heartland of the West Midlands, and one that helped pioneer much that's standard in the modern car world: synchromesh gears, front-wheel drive and independent front suspension are just a few examples. It even campaigned a front-driven grand prix racer in the 1920s.

Alvis car production wound up in 1968, but the firm transferred its passenger division to a consortium of former workers – and survives to this day as the primary place to have an Alvis meticulously maintained.

"Back then, there were no car collectors as such," says Alan Stote, who has owned the business for over 30 years. "If you had an old car, you were either poor or eccentric – those were the two criteria. Alvis wouldn't have imagined that its passenger division would need to last any more than 10 years."

Its buildings are still richly stocked in original parts (boy, could you spend hours perusing the dozens of floor-to-ceiling shelves) and all of the original blueprints and ownership records survive too. Acquire an Alvis on the classic car market now and its history will be exhaustively filed here.

"Customers will say 'I've just bought this Alvis', bring it to us, and we will give them a complete printout of the car's history from when it was new," Stote tells me. To prove the point, he casually lays out Prince Philip's original correspondence with the factory for me to flick through over my morning brew. Which I naturally move well out of spilling distance...

"We get 150 to 200 cars a year through our workshop," continues Stote. "Quite a lot of people hang onto them. They were bought by those who were interested in cars rather than just a mode of transport. It's not unusual to have a customer come in with several boxes and a ladder chassis frame saying: 'I've had this car since I was a student in the '50s, my daughter's getting married and I've promised she can go to her wedding in it.' That's the sort of thing we get."

Alvis produced around 22,000 cars during its original, 49-year lifespan, of which a whisker under 5000 remain. But under Stote's guidance, that number is slowly climbing. Alvis now runs a continuation business alongside its rich parts and servicing work.

Proffer a spare £325,000 (or so) and you can order a new car made from those bewitching blueprints, with a choice of half a dozen bodystyles and a 3.0- or 4.3-litre six-cylinder engine built to original specifications but with enough modern technology (and a slick Tremec gearbox) to help it sail through emissions tests.

You can have a new one, built as a continuation car and with a modern registration, or if you keep navigating Alvis's Narnia-like parts warehouse, you will end up in another facility, chockful of pre-loved chassis looking doe-eyed for a new owner and a fresh lease of life. It's a chance to own a shiny, reliable new Alvis wearing its original plate.

"Part of the pleasure for buyers is the journey of their build," says Stote. "They can come and see it, sit in it and be part of it. And they know the final car is unique to them."

It takes up to 5000 hours to reinvigorate an old Alvis, with nigh on all the parts being built or sourced locally. "We're in the heart of the UK automotive industry, after all," I'm cheerily reminded.

Kenilworth isn't just a place to indulge in nostalgia or unearth a curiously convenient barn find: it's a British car-making success story amid a turbulent landscape.

We drive a brand-new one

"Would you like a go?" asks Alan Stote, despite temperatures loitering below zero posing a stern challenge to the period-correct Blockley tyres of this dazzling 4.3-litre Vanden Plas continuation.

Callam Roberts is my willing assistant, the chipper 24-year-old taking a break from the workshop to show me the ropes and how easily the car dances to his command.

The modern six-speed gearbox snicks through simply and the morning gridlock is a cinch. Every twitch of your hands or feet instigates movement beneath. It's easy to see why hustling cars like this demanded notable skill in their heyday. But with a welcome dash of modernity for its more prosaic components, you can focus on car control rather than merely keeping the thing ticking over.

Its immense straight six possesses a chunky torque band: 184lb ft. It may sound modest in a car so vast, but it's present from 1000-4000rpm.

The car doesn't put a foot wrong, and nor do I. Phew. But if ever there were proof that these original-blueprint Alvis cars meet modern standards, it's this.

Autocar timed the Alvis Super Tourer from 0-60mph in 11.3sec in 1938, declaring it a supercar, and Roberts reckons it's now quicker still. Perhaps we should get the road testing gear back out...