The upcoming McLaren MP4-12C Spider will feature an innovative folding roof mechanism. The appearance of the first MP4-12C Spider on public roads backs up earlier leaked patent drawings obtained by Autocar. These revealed that the roof is made up of three panels which fold and stack on top of each other, and are then stored behind the seats in the two-seat cabin.

This creates a larger-than-normal targa-style opening in the roof and preserves the MP4-12C’s shape with the roof both up and down. It also allows the mid-mounted V8 engine to be viewed through a glass panel, even with the roof down.

The system has been developed by Webasto, the German firm that registered the patent and also created the folding roof mechanism for the MP4-12C Spider’s biggest rival, the Ferrari 458 Spider.

Like the coupé, the MP4-12C Spider uses McLaren’s exceptionally strong and rigid carbonfibre ‘Monocell’ chassis, which makes for a favourable convertible conversion.

McLaren will want to limit any weight gains in the MP4-12C’s conversion from coupé to convertible, so it’s likely the roof panels will be made from carbonfibre or aluminium.

Power will come from the same Ricardo-developed twin-turbo 3.8-litre V8 used in the coupé. The engine is good for 592bhp at 7000rpm and 442lb ft from 3000-7000rpm. Thanks to the roof’s lightweight construction, the Spider is expected to match the coupé’s 0-62mph time of 3.3sec and 205mph top speed.

The test car, spied in West Sussex close to Ricardo’s headquarters, could also be doubling as a mule for testing parts of the F1 successor’s larger V8, given the length of the exhaust pipes. They appear similar in length to those of the larger full-blown F1 mule spied by Autocar earlier this month.

Pics - Russell Hamilton