A car to rumble about in. That’s what the Interceptor does so well. It’s not a sports car, it’s a muscle car. Just one styled in Italy and built in the West Midlands. But its heart is American. Always has been.

The Interceptor arrived back in 1966, powered by a 6.3-litre Chrysler V8. It survived for a decade and three versions, until the collapse of the whole firm in the wake of the oil crisis. But in that time it heralded new technologies: the 1967 7.2-litre FF introduced four-wheel drive and ABS brakes to road cars.

What was it actually for?

It was designed as a grand tourer, a rival to the Jaguar E-Types and Aston DBSs of the day, boasting a four-seat cabin and huge boot wrapped in Carrozzeria Touring bodywork. It’s a handsome, distinctive shape, rounded off with that astonishing piece of rear glass.

It took to the GT role splendidly, but the Jensen badge never had the cachet or racing back story of Aston Martin, Jaguar and Bentley, and so values have never soared. Good. It means collectors haven’t come knocking and the Interceptor retains its under the radar mystique. Yes, the image is 70s chestwig and Soho casino, the Interceptor a car for cads, bounders and rakes, but driven today it’s hugely beguiling. Well, depending on which one you drive.

Why’s that?

Although the Interceptor had premiered high tech solutions, that wasn’t reflected everywhere. There was no monocoque construction and it had a live rear axle on leaf springs that was old tech when the Interceptor was new.

The one you see here is different. The work of Jensen International Automotive (JIA), an indirect phoenix from the ashes of the original, this isn’t a restomod as such, more an improved classic. In place of the period Chrysler V8, JIA fit a variety of Chevy LS units. Here in this flagship Interceptor R version it’s an LSA: a supercharged 6.2-litre V8 good for 556bhp and 551lb ft.

The gearbox is a six-speed auto, the brakes are from AP Racing, the front end geometry has been redone, there are adjustable dampers and it has a Jaguar-sourced independent rear end.

What’s it like to drive?

Semi-period. This is not a car that’s been burnished to a sheen. The automatic gearbox lurches the shifts, but is far sharper than the three-speed fitted originally. The chassis doesn’t feel hugely stiff, it’s still ponderous around corners, there’s a bit of shake from the trim and it generally behaves in a way that would make those who haven’t driven an old car before believe this was a 50-year old car.

Here's an alternative viewpoint: it’s one of the most engaging and charismatic ways of just rumbling and woofling around that’s ever been devised. You never feel the need to rush or push the Interceptor. The V8 is effortlessly muscular and there’s something deeply pleasing in the act of getting about the place in it. Mostly for the noise it makes, this muscular but lazy, almost soporific V8 heartbeat. It’s not rowdy or ostentatious, it’s just there, laid back but bossing it.

And when you do open the taps?

The Interceptor was never this fast in period. The supercharged JIA car hauls like a bloody train, nose up and charging at the horizon. The advantage is that unlike an original it actually tracks straight and true and remains stable and planted. JIA claims 174mph all out and 0-60mph in 3.8 seconds. We can well believe it. Although we couldn’t bring ourselves to treat it like that. Better to let the mid range do all the work. If you do insist on clogging it, you’ll be very glad JIA has equipped its Interceptor with ABS and traction control. Turn it off and this will demolish rear tyres like a wrecking ball swinging at a rabbit hutch.

How’s the cabin?

A palace of brown magnificence. It’s airy inside, the leather creaks, the colour scheme is period-perfect, the seats are deep and welcoming. It’s very comfortable on long trips.

There are a few quirks that time has left behind: the ignition is in the centre console rather than the steering column, and if you press the footrest you will discover it clicks. It’s the switch that activates the main beam. There’s surprising room for four inside and the boot is utterly enormous. We must assume four-up trips to the golf course with a bag each were de rigueur back then.

What will one set you back?

An original can be anywhere from a £10k basket case to a £90k minter, but most hover around the £30-£45,000 mark with the scarcer convertibles fetching upwards of £10k more. But not stupid money. As we said, this is not a car that’s ever captured the zeitgeist. Just be aware of the investment required to restore and maintain one.

The JIA car, a product of thousands of hours of skilled labour, comes with the restoration sorted and complete mechanical peace of mind. But it’s silly money: £390k, which means it’ll only ever be a car that appeals to wealthy, died in the wool Jensen enthusiasts. More detail on that in the Buying section.

Ollie Marriage

Ford Focus ST meets the fast Ford ancestors

BMW M5: a fond farewell

BMW M5 vs Mercedes-AMG E63S

How well does the BMW M5 drift?

BMW M5 vs the rivals

Is the BMW M5 practical?

Our BMW M5 is broken

BMW M5 or Alpina B5?

Is the BMW M5 a luxury car or a sports saloon?

BMW M5: TG's long-term review

Audi S4 Avant review: a half-price RS6?

How to buy a British sports car on a budget

Opinion: Nissan's GT-R is a better all-weather car than the Audi RS6

Progress report: Audi RS6 2002 vs 2008 vs 2013

We've bought a Peugeot 306 Rallye so you don't have to

Range Rover Sport review: P400 HST kinda-hybrid driven

Toyota Supra vs BMW M2 vs Alpine A110 vs Porsche Cayman

Here's what it's like living with a Mercedes EQC for a weekend

Ten things we learned about the new Land Rover Defender

Merc-AMG A45 S vs Audi RS3: 0-120mph battle

The next Merc-AMG C63 will be 4WD and get Drift mode

EU to ban rubber after carbon fibre u-turn

Rolls-Royce has revealed the Rolls-Royce of chess sets

For sale: the rare, yellow, ex-Ralph Lauren Ferrari F50 that disappeared for 16 years

Here are 10 cool used cars for around £30k

Nissan GT-R T-spec review: the Goldilocks Godzilla you can’t buy

Meet your heroes: the Jensen Interceptor is a Great British muscle car

Subscribe to the Top Gear Newsletter

Subscribe to BBC Top Gear Magazine