Both cars share the same 542bhp 3.0-litre straight six, plus the punchy stripes adorning a full-carbon bonnet, as well as having standard-fit carbon-ceramic brakes.
The CSL also donates its titanium exhaust silencer, which hangs provocatively from the CS’s reprofiled, carbon apron. Under the skin, the CS has a bespoke tune for the damping, springs, DSC, steering and brakes.
Inside, there’s a new, Alcantara-clad steering wheel with a quite subtly squared-off base, as well as the pared-back carbon-finished centre console from the CSL and mighty bucket seats.
It’s a fabulous cabin – perhaps, for a track-day-type creation, a touch dominated by the displays, but serious all right.
The driving experience is pitched squarely between M4 Competition (10sec slower on the Nordschleife) and CSL (4sec quicker). However, the decisive element is a driven front axle – so notably absent on the fighty CSL.
The resulting car is, on acquaintance, a real honey. The M4 CS’s date with a damp B-road will have to wait, but on the Salzburgring – a lumpy circuit that is more useful than most for unravelling road cars – the CS sings.
Anybody coming from a lower-slung, more dedicated sports car will need a moment to adjust to the BMW’s freer vertical body control and lighter steering, but the confidence the car quickly instils is a joy.
More easy-going on-throttle adjustability – not quite to the CSL’s mad levels, but not far off – would surely come with less sticky tyres than the optional Michelin Cup 2 R rubber fitted to our test car.
Even as is, the CS wants to take a silken touch of yaw in all the right places. Elsewhere, the unflustered accuracy on turn-in, its mid-corner stability, then huge traction on exit combine to make seamlessly smooth, devastatingly quick lines easily achievable and rewarding.
Four hot laps go by in a flash and that’s our lot. Could the car feel a touch lighter, its brakes a tad more resolute, its steering feel a smidge grainier? Sure, but the big picture is one of a class-leading sports coupé, and by some margin. Only 100 of these will be coming to the UK.