The sighting shows that the model, which will be revealed on 28 June, will follow suit of the 675LT and recieve a 'long tail' (hence the name) to enhance aerodynamics. This change harks back to the McLaren F1 GTR 'long tail' that was produced for endurance racing in 1997.
Along with a modified body, the 600LT will use a more potent version of the 570S's 3.8-litre twin-turbocharged V8 producing 592bhp (600PS) and breathing through a lighter and less restrictive exhaust system.
The tailpipes for this exhaust will come through the car's engine cover, as seen on the test car and previewed up close in an earlier official image (see gallery).
When revealing its official pictures, McLaren confirmed that it has reduced the 600LT's kerb weight — the standard 570S weighs 1440kg — but it has yet to reveal a figure. The 675LT shed 100kg from the 650S it is based on, suggesting the 600LT could tip the scales at less than 1350kg.
The harcore Sport Series model, which was scooped by Autocar in March, will make its public debut at the Goodwood Festival of Speed, when it will be driven up the famous hill climb.
Production of customer cars will be “limited to the few”, suggesting the 600LT will be made in similar numbers to the 675LT Super Series model, of which just 500 were made.
Because it belongs to the Sports Series, the new car is unlikely to receive quite the same extent of obsessive attention as the 675LT, which added more than £65,000 to the price of the £195,250 650S on which it is based and included 110 component changes or deletions just to save weight.
But we could still see a car with a price that's up from the 570S's £149,000 at something nearer £200,000, before customers start splurging on lightweight carbonfibre options. Expect lighter wheels, reduced sound deadening, the titanium exhaust that's already available through McLaren’s MSO department, thinner glass and perhaps a Perspex rear screen.