The little door flips up to reveal an impossibly wide sill for you to step over. But step you do and, taking care over where to put your hands and feet on this museum piece, you lower yourself into the seat. It’s all so simple: a rev-counter ahead, flanked by readouts for oil pressure and temperature. A small leather-lined wheel with perforated spokes, a simple right-hand gearchange, three pedals and that’s about it.

What could be easier? Pull one button, press another to start the engine, select first gear, raise the clutch and off you go. Given what these controls are actually attached to, it’s all so prosaic it’s almost mundane. But of course, that’s the way it’s meant to be; in a car like this, keeping things as simple as possible is not merely desirable, nor ever just important. It’s essential.

“Second gear runs to over 100mph, third to better than 150mph and fourth to 225mph”

Because this is the Porsche 917/30 and, over half a century since one last raced in period, it is at least arguable that it remains to this day the most powerful car ever to have competed – rather than just merely qualified. And my job is to try to convey to you just what 1100bhp in a car weighing a mere 850kg is actually like.

The car I am in is the prototype, one of just three such cars that raced in the ’70s, the other two more famously in Sunoco colours in Can-Am. This one was no less dominant in Europe’s Interserie equivalent: there were six rounds in 1974, it came second in two and won the rest. It raced once more in 1975 and won that too, so it is not only the first 917/30, but also the last to race in period.

And the easy thing to say was it was all down to that 5.4-litre, twin-turbocharged, flat-12 engine in the back and its aforementioned monstrous output. But it’s not as simple as that: even the most powerful missiles need to be guided and it’s actually here, rather than in the headline figures, that the 917’s real secret can be found.

But until you know that, I’m happy to share that it is utterly terrifying. Second gear runs to over 100mph, third to better than 150mph and fourth to around 225mph. Vic Elford raced this very car and told me how impressed he’d been to change up to fourth, put his foot down and still see black lines of molten rubber laid down behind the car.

You have to build up to it. I’m on the International Circuit at Silverstone, with no instructions whatsoever from Porsche Classic who have brought it here today. But obviously I’m not going to be banging it up the kerbs and I decide to keep about 1000rpm shy of peak power out of respect for its age. Forget putting your foot down in first and second gears for they would boil the vast rear tyres in a heartbeat. I’m wary of third too, thanks to Vic. So as I enter the Hangar Straight, I select fourth and gently, tentatively, put my foot down. Cough, splutter, bang, splutter. It’s not happy and there’s no great surprise in that: thoroughbred racing cars rarely take kindly to the softly-softly approach.

So on the next lap the foot goes all the way down. You expect there to be an explosion behind you, for everything to go white and to wake up in hospital, but that’s not what happens. The mighty engine growls a bit, then starts to roar, accompanied by the great whooshing sound of the turbos spooling up. But you can feel it coming, so when it arrives you’re ready for it; or as ready as you’ll ever be. And yes, the Hangar Straight does sort of evaporate and I’ve never seen the Stowe grandstand grow so large so quickly, but actually? It’s manageable. Just about. The secret is that the engine is not actually boosting that much. There’s at least one 2-litre, four-cylinder hatchback on sale today which generates more horsepower per litre. So that feel is as much 5.4-litre flat-12 as it is a couple of turbos the size of dustbin lids. It’s almost progressive.

“Cough, splutter, bang. Thoroughbred racing cars rarely take kindly to the softly-softly approach”

Even that is only part of this car’s secret. By the time it was in its pomp, the 917 had been in development for four years, going from what Richard Attwood told me was “the worst racing car I have ever driven” in 1969, to what Mark Donohue described in 1973 as “the perfect racing car” despite its power having nearly doubled. He didn’t say that because it had 1100bhp per se. He said it because it had 1100bhp and could handle it.

Not once in all those laps did it suggest it might even want to nibble at me, let alone take a proper bite. It is rock stable at 150mph, its brakes as good as you could hope from such a car with zero downforce, and partly because its wheelbase was extended over that of its predecessor, the less powerful but more difficult 917/10. You feel you can actually press on through the corners without coming to regret it.

Porsche 917/30

• Engine 5.4-litre twin-turbocharged flat-12
• Chassis Aluminium tubular spaceframe with glass-fibre-reinforced plastic body
• Power 1100bhp
• Transmission Four-speed manual gearbox
• Suspension (front & rear) Double wishbones, coil springs, shock absorbers, anti-roll bar
• Weight 849kg

And then it does that racing car thing. The faster you go, the easier it gets. This is a car designed only to be driven flat out, with tyres, brakes, shock absorbers and all fluids fully up to temperature, and when it is you discover it’s an absolute delight to drive too.

That had never occurred to me before I first drove the 917/30. I knew it would be an unforgettable experience, a challenge and that I’d need to be at my best to drive it safely, but I had expected it also to be something I would enjoy only having done it. Surely I’d be too busy/terrified at the time? Not so. It was like falling into a gorilla enclosure and seeing a silverback come thundering up but, instead of tearing you limb from limb, he sits down next to you and offers you his banana. And a mighty tasty one at that.