Lambo Aventador J is King

Everyone knows Rome wasn't built in a day, but did you know the Aventador J - Lamborghini's outrageous speedster that brought Geneva to its collective knees last week - was cooked up in just six weeks?

After scooping our mandibles from the floor after Lambo whipped the covers off the roofless, screenless J, Top Gear secured an exclusive interview with designer Filippo Perini for the full story behind the lowest Lambo in history. It's fair to say he looked a little rushed. This is why...

Though the Aventador J was widely reported to have been commissioned by a well-heeled customer, Perini reveals it was devised entirely in-house by the Lamborghini team after CEO Stephan Winkelmann asked them to come up with ‘something special' for the Geneva show. As is traditional at Lamborghini, this required some fairly rapid forward progress.

Gallery: the Lamborghini Aventador J

"It was the 14th of January that Mr Winkelmann asked us to do something for Geneva," says Perini. "A blank sheet. Do what you want. I drew up this car in a weekend..."

So that's just a month and a half to bring a car from drawing board to reality: most companies would take that long to decide on the level of damping on the stereo volume knob.

The timeframe is even more astonishing when you consider that the J is far more than an Aventador with the roof and windscreen lopped off. Only the front bonnet, front fender, rear fender and headlights remain from Lambo's big V12 coupe: every other panel is new.

A huge winglet-covered diffuser lurks at the front, while the rear diffuser has grown too, and sprouted a quad of evil exhausts (imagine the noise). The Aventador coupe's slatted rear deck is gone, replaced by a pair of sleek humps and a delicate carbon-fibre crossbrace over the engine. And just look at that ‘periscope' rear-view mirror.

Six weeks. And don't forget this is no concept: the J is road-legal, homologated in Italy (we're not sure how the single-car homologation procedure works in Italy, but we'd imagine it goes something along the lines of, "Yeah, it's a massive red Lamborghini with no roof. Any problems? No? Great...").

Even before its Geneva unveiling, the one-off J had already been sold, to an anonymous but presumably not-very-poor Lamborghini enthusiast.

"Mr Winkelmann knows our best customers personally," says Perini. "One of the first ones we presented the project to was interested. In a minute he had sent the money."

Well, what self-respecting businessman doesn't have £1.75m (plus taxes) sitting idly in his current account? And has our supercar value scale got a bit skewed recently, or does that not sound like such a ridiculous price for Lamborghini's most extreme one-off since 1970's Jota?

The common ‘J' is no coincidence. Though Lamborghini claims the Aventador J's suffix refers to the FIA's ‘Appendix J' regulations, the rulebook governing technical specifications of sports cars and their homologation requirements, this is a lie. It's short for Jota, the Miura-based racer that remains, even today, Lambo's most extreme, iconic creation.

"I have always wanted to do something with the ‘Jota' name," Perini says. "Inspiration comes from the past, and the Jota is the true heritage of our company."

A worthy successor? A snip at one-point-seven-five-million-plus-taxes? Or simply the most depraved piece of automotive smut this decade? For the full story behind the Aventador J - and a photoshoot we guarantee will make you feel a bit funny-in-a-good-way - make sure you pick up the April issue of Top Gear magazine, on sale 29 March...