The engine gets its own mapping and loses its secondary catalyst, which is why it is able to develop 814bhp, a rise of 25bhp over the road-going Senna and taking the engine past the 200bhp per litre mark.

The interior is that of a pure racing car – pared to the bone, and all major controls are mounted on the sawn-off steering wheel where they can be reached without stretching (not possible when you’re clamped by a six point harness) and operated easily by a gloved hand.

Strangely, it is only 10kg lighter than the Senna, though at 1188kg dry it is the lightest McLaren coupé since the F1. The weight lost by the simpler suspension, stripped interior the removal of the catalytic converter and its airbags is almost entirely offset by the additional bodywork, data logging systems, the on board air-jacks and fire extinguishing system. It costs £1.1 million before tax.

What’s it like?

The truth is that however wonderful is the Senna road car, it is held back by the need to use a street-legal tyre, even one as sticky as a Pirelli Trofeo R. Shorn of that requirement and given full race suspension and even more aero, the Senna becomes uncorked and an entire new dimension of deftly controlled lunacy awaits.

In the very damp conditions I encountered it would spin even its super soft wet race rubber at any speed you chose, up to I guess at least three-figure velocities. But the traction systems are so good you don’t need to fear using the power: it will give you what you can use and no more. You can hit the brakes hard too at high speed, because there’s a family hatchback of downforce pressing the car into the Tarmac too.

Because it had a full dry suspension set-up and was consequently very stiff, grip levels in slow corners where the aero barely works is not spectacular, but not only is it not scary when it slides wide under power at the exit, it’s fun.

McLaren reckons the Senna GTR is 3-5 seconds a lap quicker than the 720S GT3 car depending on circuit, and would be quicker still were it not required to use quite hard slick tyres and be configured for mere mortals rather than professional racing drivers.