If you want to properly understand the million-dollar McLaren Senna supercar, you've got to make the pilgrimage to Woking, just southeast of London. There, you'll find McLaren’s UK Technology Center headquarters. What looks like a science fiction movie prop dropped into the English countryside is in fact home to the factory hand-building road cars—and McLaren's Formula 1 team. The kidney-shaped structure wraps floor-to-ceiling glass around a pool of tranquil water, which is used for cooling the mechanics when a huge onsite wind tunnel is running.

It is, that is to say, exactly the sort of place that would produce a car like the Senna, which promises to be one of the world's most radical road machines. The 4.0-liter V-8 engine, sitting behind the two carbon fiber seats, produces 789 brake horsepower, a whole lot in a car that weighs just 2,461 pounds. It's also the sort of place where your tour guide confirms that yes, that's Fernando Alonso who just walked by. He's there doing interviews before the F1 season kicks up, but you wonder if McLaren keeps him around to remind visitors that it's been in the sport for 50 years.

Inside, a wave of a hand over a hidden sensor causes a section of wall to glide open, revealing new curved corridors. Another hidden, swooshing door reveals the back of the house, where a brand-new McLaren Senna sits on a turntable.

“For us, it’s a real treat to be able to spend some quality time with a real vehicle, a production car,” says Mark Roberts, McLaren’s design manager, explaining that he’s happy to take time out of his day to show me around the car. Normally, he sees a vehicle as a clay model in the studio, perfects it, then moves on to the next project. There's not much time built in for looking back.

With the Senna, the million-dollar base price buys you less, not more. It’s stripped back, bereft of everything that adds weight. All that's left is a passenger cell, shrink-wrapped in carbon fiber, with an enormous wing on the back. “It’s like the car’s been working out in the gym; it’s showing the structure and the skeleton underneath that,” Roberts says.

This machine is all about performance and sits at the “ultimate” end of the spectrum of road cars that McLaren has produced for just 25 years, dating back to the revolutionary three-seater F1, then the P1 in 2012. The company also builds the slightly more reasonable “sports” series with the 570S, and the “super” series with the 720S.

The Senna unashamedly prizes function over form. The resulting extreme looks are polarizing but look more cohesive in the flesh than in photos. Waving his hands over the car, design engineering director Dan Parry-Williams shows how air gets sucked around the squared-off front splitter and through the wheel arch. The cutaway design of the door accelerates the airflow, steering it down the side of the car. “We pushed the door in as far as possible, right into the structure,” Parry-Williams says.

It's one of many techniques his team used to generate a phenomenal 1,763 pounds of downforce, the thing that keeps the car glued to the road in the corners—key to performance. “The car grips in every situation; it’s pretty much like an F1 car,” Roberts says. More help comes from that giant surfboard-like wing on the back—a full 4 feet off the ground—and the car has active, steerable, aerodynamic elements to deflect air and shrug off some of that downforce when it’s not needed, like when pelting down a straight when it would just be drag.