The McLaren 600LT is the fifth and most powerful model to be added to the British brand’s Sports Series range. It will be hand-built in limited numbers and cost from £185,500.

McLaren’s LT sub-brand, short for Longtail, is reserved for only the company’s most extreme models. Only four cars have carried the badge, starting with the McLaren F1 GTR racer in 1996.

The 600LT adopts the 675LT’s mantra of more power, less weight and optimized aerodynamics. Under the skin the car is based on the 570S coupe but McLaren claims almost 25 per cent of the car’s parts are new or redeveloped.

The bespoke carbon fibre bodywork is the most obvious change over the standard model; the body itself has been stretched by 74mm thanks to a unique carbon fibre roof, front splitter, side skirts and extended rear diffuser. Along with a fixed rear wing, the changes allow the 600LT to produce 100kg of downforce at 155mph.

Changes continue inside where McLaren has fitted carbon fibre racing seats from the P1. Trimmed in Alcantara, they save 21kg relative to the items fitted to the 570S, though buyers can go one step - and £4,990 - further and spec even lighter carbon fibre seats borrowed from the Senna. A lack of carpets sheds 5.7kg, and the exclusion of air con, satellite navigation and hi-fi help trim the overall mass further - though all three are still available as no-cost options.