It weighs only 40kg more than the coupé but offers near-identical performance, zero to 62mph taking 3.0sec and 0-100mph taking an F1-demolishing 5.7sec (we recorded 6.3sec in the old timer when we road tested it in 1994).
Top speed is the far side of 200mph while emissions and economy are actually a touch better than in the 12C – impressive considering the gains in both power and torque.
As many as 25 per cent of the parts are new compared with the McLaren 12C Spider. Carbon ceramic brakes become standard fitment, the seven-speed dual-clutch automatic gearbox has been tweaked to deliver more responsiveness and so has the 3.8-litre twin turbo V8 engine, which now produces 641bhp and 500lb ft of torque between 3000-7000rpm.
But most important of all, claims McLaren, the character of the car has become considerably more hardcore, without levels of refinement being significantly affected.
As such, there's more engine noise than in the 12C, the brakes have more feel (particularly under light loads), the suspension is more urgent in its response and turn-in is considerably more incisive as a result, says McLaren. There's also the option of new sports seats, which are lifted virtually unchanged out of the P1.
McLaren says that, despite obvious comparisons, the 650S coupé and Spider aren't direct rivals for the Ferrari 458 Speciale as the car isn't intended to be quite as focused.