The top-secret McLaren X-1 concept has made a dramatic debut at the 2012 Concours d’Elegance in Pebble Beach, California, giving the world an exclusive look at the extreme one-off supercar creation.

Developed by McLaren Special Operations (MSO) – the division of the Woking, England-based sports car manufacturer responsible for the design and production of bespoke projects – the X-1 concept has been three years in the making from initial conversations to the finished product.

MSO program director Paul MacKenzie said an anonymous client approached McLaren chairman Ron Dennis in 2009 asking for “a machine that had all the capability of the [MP4-12C] but wrapped in a unique body that reflected his needs and personality”, and one that would stand out in his garage that includes a McLaren F1, a Mercedes-Benz SLR McLaren and an MP4-12C.

In a three-hour meeting with MacKenzie and McLaren design director Frank Stephenson, the client was presented with hundreds of images from the world of automotive design, architecture, fashion and film before narrowing down a mood book filled with ideas from which the vehicle’s design spirit would be derived.

Included in the client’s mood book were images of the 1939 Mercedes-Benz 540K, 1953 Chrysler D’Elegance Ghia, 1959 Buick Electra, 1961 Facel Vega and a 1971 Citroen SM, as well as images of the Guggenheim museums in New York and Bilbao, a Jaeger LeCoultre art deco clock, an Airstream trailer, a Thomas Mann Montblanc pen, a grand piano, a black and white photo of Audrey Hepburn and – perhaps most intriguingly – an eggplant.

“The client liked the shiny texture of the finish,” Stephenson explained.

The client demanded a competition between designers from around the world from both within and outside of the automotive industry, and ultimately selected a design by McLaren’s own Korean-born designer Hong Yeo.

Yeo explained one of the greatest challenges was developing a design that embodied the elegance of the client’s preference for classic cars with front-engined, rear-wheel-drive layouts around the MP4-12C’s mid-engined construction.

The styling took 18 months to sign off, with the client finally satisfied the MSO team had achieved perfection.

“X-1 embodies the McLaren value that every part has to have a purpose,” Yeo said. “No details are simply visual cues, every one has a purpose.

“I like to think the wide body combined with pontoon style rear fenders will ensure the car glides when it’s moving just like a superhero’s cape.”

With the X-1 concept’s entire body, including its lights and wheels, almost entirely bespoke, MSO began testing and homologation work two and a half years ago, long before the design was finalised, as the client required the car to be usable, road-legal and capable of travelling at supercar speeds.

The McLaren X-1 concept’s body panels are constructed from carbonfibre and finished in piano black lacquer. The body’s brightwork is machined from aluminium and finished with nickel, as are the diamond-turned wheels, the rear airbrake and the McLaren Speed Marque badging.

The carbon panels enclosing the rear wheels are perhaps the most striking element of the design, which Stephenson says feature “some of the most gorgeous hinges you’ve ever seen”. The doors and roof were also specially developed for the X-1.

The unique body makes the X-1 concept 109mm longer and 188mm wider than the MP4-12C, but is the same in height and weighs an almost identical 1400kg.

The basic architecture of the interior did not change, although personalisation options include Harissa Red nappa leather, nickel-coated aluminium bezels, titanium-weave carbon trim and andesite tufted floor carpets.

The mechanical package is lifted straight from the MP4-12C production car, with its twin-turbocharged 3.8-litre V8 continuing to produce 460kW of power and 601Nm of torque.

Stephenson said the McLaren X-1 concept was the ultimate expression of the company’s ability to tailor a unique product and enable the client to become an integral member of the design team.

“It has been a truly rewarding and unforgettable experience.  And I think that we as a team have created a completely unforgettable car that is true to one man’s vision.”

Following its Pebble Beach debut alongside the McLaren MP4-12C Can-Am Edition, the unpriced X-1 concept will return to MSO’s headquarters in Woking to be carefully checked over before being placed in the client’s collection.

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