Speaking to TopGear.com at the Geneva motor show, Koenigsegg spokesman Andreas Petre confirmed that just six of the extreme hypercars were built - seven if you include the company's own R&D car - with two being sold to British customers, and four on their way to China.

In fact, it was the Chinese who initiated the One:1 concept. "It was actually our Chinese distributor in Beijing who told us he had a group of customers who want a track car," Petre tells us. "They had every other kind of car, but they wanted a Koenigsegg track car."

This being Koenigsegg, company boss Christian obliged, under the proviso the car remained street legal. "We had to decrease the weight, increase the power significantly, include all the goodies, air conditioning, stereo, central locking, ESP, ABS, electric windows... all these things had to be integrated into the car and make it lighter," Petre reveals.

The result is quite a thing, you'll agree. It's got a "dream" equation of one hp per kg - hence the name, One:1 - and is the world's first homologated production car to produce a full MEGAWATT of power. Great Scott, indeed.

There's a Le Mans-inspired active wing configuration that produces around 600kg of downforce - the same as the P1 - larger air vents for cooling, active undertrim air management, a roof air scoop, titanium exhaust system, upgraded triplex suspension with carbon bevel springs with active shocks and ride height, and of course, an upgraded version of the twin-turbocharged 5.0-litre V8 from the Agera R.

"Top speed is around 440km/h, it'll go from 0-100km/h in 2.8 seconds, 0-300km/h in about 12 seconds and 0-400km/h in 20 seconds," Andreas told us. "We didn't set out to build the Agera One:1 as a top speed car, so that theoretical 440km/h was a bit of a gift to us.

"We'd like to do a top speed run but it's not a priority. I think a track time is much more important. I mean, the Nurburgring is the only lap time that really counts. I mean, if we also had access to the NASA landing strip in the US, we'd probably go at least as fast as that Venom GT. Obviously his [Hennessey's] top speed run is great for him, and I mean no disrespect, but we think the GT is a different sort of concept to the Agera One:1."

Still, even though you can't buy it, you'll be able to buy a form of it. "We'll have the 2015 Agera up next - essentially a facelift - but it will feature a lot of the One:1 technology: the active chassis, the rear wing, the suspension, everything," says Petre. "All of that will go in the normal production car which you'll see at the Geneva show next year. We see the Agera as more of a 911 sort of car - one that evolves slowly over time..."

So where does Petre see Koenigsegg in a few years' time? "Ferrari and Lamborghini used to be like us, they used to build around 100 cars a year, but they became a bit more commercial. My boss is a bit more family orientated, he likes to keep it more as a family sort of business, and he likes to be closely connected to the customers, so I don't think we'll go the way of the others...."