Based on the 570S, the track-focused McLaren 600LT is the most hardcore Sports Series car McLaren has ever built, but it's about to get even more extreme. Leaked photos obtained by PistonHeads show that McLaren is cooking up a new hardcore supercar called the 620R based on the McLaren 570S GT4 race car. And unlike the Senna GTR, this beast will reportedly be road legal, essentially making it a race car for the road.

When contacted by Pistonheads, McLaren confirmed the 620R will be offered to "select customers by invitation only," which suggests production will be extremely limited. Chances are it will only be offered to customers who already own the 600LT. Its limited availability and race car roots mean we can also expect it to cost a lot more than the 600LT, which starts at a wallet-crunching $240,000.

From the photo renders sent to Pistonheads, it's clear that we're looking at a significantly more hardcore version of the 570S. Whereas the 600LT was based on the road-going 570S, the 620R is based on a thoroughbred racecar, and it shows. Aerodynamic components such as the prominent rear spoiler, front splitter, intake arrangement, and diffuser are derived from the 570S GT4. Front aero flics also highlight the 620R's racing roots, and the car appears to ride on the same 18-inch magnesium wheels as the race car. Elsewhere, the 620R features a new roof scoop and ditches the LT's direct-exit exhaust.

Unsurprisingly, the 620R sits much lower to the road than the LT as a result of inheriting the GT4's coilover springs and adjustable dampers. Carbon-ceramic brakes will almost certainly be offered too, to give the 620R supreme stopping power. No photos have been released of the cabin, but we're expecting the interior to be stripped out to save extra weight and feature bucket seats, track telemetry, a racing-style steering wheel, and copious amounts of carbon fiber.

As for the powertrain, the 620R should pack even more power than the 600LT. Whereas the 600LT's 3.8-liter twin-turbo V8 pumps out 592 hp and 457 lb-ft, the model name suggests the 620R will increase the output to around 620 hp since it will be free of GT4 racing restrictions. That would make it the most powerful Sports Series car yet and a fitting swansong for the 570S.