The most extreme Porsche Cayman to come through official channels was the delicious GT4. With a 3.8-litre flat-six lifted from the 911 Carrera S (producing 380bhp at 7,400rpm) it was the most potent Cayman ever. This mid-mounted engine was fused to a six-speed manual, and only a six-speed manual, plus dynamic gearbox mounts and suspension bits from the GT3. It was the Cayman to rule them all. Actually, it might be the Porsche to rule them all.

Though Porsche had to tread with caution. For years, the German brand stymied the performance of the Cayman to prevent it trampling on the toes of big-brother 911. What, you might reasonably wonder, would happen if you properly let the young pup off the leash? We suspect something like the car above: M’s Machine Works’ bonkers Cayman GT3.

It’s the work of Takayuki Mizumoto, a Japanese motorsport engineer who lives to cut tenths from a lap time – no matter how mad the process. His day job is running M’s Machine Works, a firm that designs, builds and manufactures bespoke components for the mad Super GT race series, the fastest race series in the world for road-going cars. How fast is fast? Put it this way, Maserati tried to enter its MC12 racing car a few years back into Super GT500 but it was deemed too slow (by almost a second a lap, entirely down to aerodynamics in corners).

Mizumoto-san’s Cayman isn’t work, though. It’s play. Loving racing as much as he does, he got a 987 Cayman S then went to town on it to make it utterly dominant around Japan’s racetracks as well as being fully road-legal. Talk about a busman’s holiday.

First up, its engine. And what an engine: a 3.8-litre lump from a 997 911 Cup car complete with carbon goodies good for 450bhp (as well as being quite the treat for your ears). Mounted mid-ship. Yep, Takayuki Mizumoto beat the Porsche factory team to putting this engine in-between the wheels. Then there’s its face, which might look quite familiar. Largely because it’s a transplant from a 997 GT3, complete with a bespoke carbon splitter, dive planes and a new flat floor. To change the track widths and add more aero, there are those silly-wide arches you could hide in and that rear wing. It’s one of the most stupendous aerodynamic appendages we’ve ever seen on a road car and straight from the GT500 parts catalogue. Downforce? It’s got it alright.

The whole car reeks of motorsport. It’s completely stripped out with a welded in roll cage, a carbon steering wheel fit for Le Mans, built-in air jack system, polycarbonate rear, side and door windows, FRP front bonnet, boot and doors. Standing on the scales it’s 100kg lighter than a GT4, which was already a stripped-out Cayman. A Motec ECU is the car’s new brain while a six-speed manual transmission remains. But there’s a trick slippy diff, proper posh custom suspension set up and super sticky Advan rubber wrapped around Volk racing centre lock wheels.

“We have been running Porsches from back in the air cooling days,” Mizumoto-san says. “We have also participated in numerous races. Without limiting ourselves as a privateer, when we needed parts of high accuracy we made them with our own hands.”

It’s the personal touches we like. Obsessed with golf and Nike’s famous swooshy branding, Mizumoto-san decided to cover the car and various parts using the tick from your favourite trainers. Then there’s the space between the A and B-pillar, now a mantelpiece to publish the car’s lap records. And there’s a few of them. Take for instance Tsukuba. The plucky Cayman managed a 58.070 with Isao Ihashi at the wheel. For reference, an R35 GT-R Nismo lapped the same track in 1:00.29 and the Cayman’s bigger 991 GT3 RS brother managed a 1:00.70.

But this is just the beginning, as Mizumoto-san is planning on making an identical Cayman, just with a twin-turbo GT2 engine instead. Yikes.

Photography: Mark Riccioni