What's all this about?

It's the BMW Z4, third generation, undergoing some final testing at the German manufacturer's south of France test base, which is called Miramas. Although heavily disguised and quite a few months ahead of the expected commencement of production, we already have some salient facts about the Z4 Mk3.

Such as?

Well, what should be obvious for a start is the material the roof is made out of - fabric, rather than metal. That means the Z4 has reverted to the type of the original Bangle Z4 of 2003, rather than the SLK-mimicking second-gen Z4 with its folding tin-lid. But the other proportions - short overhangs, long bonnet, rear-slung passenger compartment - are all classic roadster and classic Z4.

Do we know anything else about it?

Jointly developed with Toyota, which will sit its forthcoming Supra sports coupe on the same chassis and underpinnings as the BMW, the disguised Z4 prototype is going through driving dynamics testing at Miramas. The German brand has already confirmed one model of Z4, called the M40i, which means the inline-six turbocharged 3.0-litre petrol engine with 340hp/450Nm that's widely in service within the company's products at the moment. BMW also says the M40i has lowered sports suspension with electronically controlled dampers, a newly-developed front axle, M light alloy wheels with mixed-size tyres front to rear, an uprated M sports braking system and an electronically controlled limited-slip differential.

Any words from the team behind the Z4?

Indeed there are. Jos van As, head of application for suspension, said: "The vehicle concept of the new BMW Z4 is geared consistently towards agility and driving dynamics. The high level of body stiffness and the very rigid suspension attachment provide the perfect basis for a set-up that guarantees the performance qualities of a genuine sports car in terms of steering precision as well as longitudinal and transverse acceleration."

And when will we see it on the roads?

The Z4 should hit the streets in the UK in the first half of 2019.