What's all this about?

It's only fabled German tuning house Brabus going utterly mental once again.

What has it done now?

Oh, nothing much. Just turned the 630hp/1,000Nm Mercedes-AMG S 65 Cabriolet into the world's fastest, most powerful four-seater open-top. This lunatic machine is the brilliantly-named Brabus Rocket 900 Cabrio and that 900 refers to... yup, the output in pferdestarke (PS), which we render as 'hp'. Thus, 900hp at 5,500rpm.

I'm sorry - 900hp?!

Correct. Or 888bhp, if you want it in old money. That's a 43 per cent output increase on a motor that was colossally powerful in the first place. But, even better, torque has gone up 50 per cent, the Rocket's motor capable of 1,500Nm at 4,200rpm. Sadly, that figure is a test-bench number, as Brabus has to restrict the engine to 1,200Nm in the car - presumably to stop the Rocket from lunching its propshaft the very first time the loud pedal is hit by the owner.

So I'm guessing this is a bit more than just a remap of the S 65's V12?

Er, just a bit. The 6.0-litre biturbo lump is bored and stroked out to 6.3 litres, and Brabus has fitted a billet-steel crankshaft, precision-balanced conrods and a set of forged pistons. The engine management system obviously has been reworked to cope with all this madness, but more hardware changes incorporate work on the intake and exhaust to ensure plenty of cool air flows in and the combusted air of a 900hp V12 floods out nice and easy. Redesigned exhaust manifolds, larger compressors and turbines for the twin turbos, 80mm downpipes, free-flow metal catalysts and a Brabus high-performance exhaust with active flaps deal with the, well, exhaust side of things. An intake duct on the bonnet rams great volumes of air into a reshaped intake manifold and filter box. Gold heat reflection wrap for the intake pipes helps to keep the charge-air cool.

And can I presume the brakes and suspension are altered to cope?

Well, Brabus doesn't actually talk about the former, although we reckon - good as the S 65's stoppers are - something must have happened to at least the pads on the Rocket 900. A lowering kit that's specially calibrated to the Brabus' large alloys and Continental tyres drops this ultimate S-Class 15mm lower than the S 65. Incidentally, all this power and torque still flows to the rear wheels alone via a seven-speed automatic gearbox, with a 40 per cent locking limited-slip differential thrown in for good measure.

What's the performance like?

On paper, the Rocket 900 doesn't look to have done much for the 0-62mph time, besting the S 65's sprint of 4.1 seconds by a mere two-tenths, at 3.9 seconds. But that's going to be down to the Rocket's traction-related issues from a standstill, no doubt; imagine trying to flow 1,200Nm to the tarmac in first or second. Wheelspin. Lots and lots of wheelspin... or manic traction control instrusion, one or the other. Anyway, once up and on the move, an additional 270hp and 200Nm are surely going to make themselves felt, the Brabus likely to leave the AMG comfortably behind. More relevant is the top speed. On the S 65, it's limited to 155mph as standard and owners can opt to have that raised to 186mph; it's very likely the 630hp V12 Merc could crack 200mph, derestricted. But Brabus says the Rocket 900 will go 'in excess of' 217mph - which is hypercar velocity. Hence the 'fastest, most powerful four-seat open-top' claim.

Can you just go over the visuals briefly?

Sure. On the outside, high-gloss carbon fibre is used for the front splitter, air intakes, door mirror caps, rear diffuser, the side air vents in the back bumper and the lip spoiler on the boot lid. The Rocket 900 wears subtle 'B', '900' and Brabus exterior badging, plus a set of ceramic exhaust outlets and 21-inch Monoblock Platinum Edition forged alloys with 255/35 front and 295/30 rear tyres. A set of max-bling 22s are an option.

And inside?

The cabin of the Rocket 900 Cabrio can be specified bespoke to customer order, but Brabus is going to take a car to the Frankfurt International Motor Show (IAA), which will sport Mondial Vanilla/Mondial Black leather with decorative, black-and-red top-stitching, Brabus-branded aluminium paddle shifts, pedals and door pins for the central locking, a Brabus-logoed steering wheel with a 12 o'clock marker, hand-made black ash wood inlays and trim strips in the fascias, illuminated Brabus scuff plates in the sills... oh, and a speedo that reads up to 250mph. Obvs.

How do I go about buying one, and how much will it cost me?

Well, presuming you've won the EuroMillions, it's likely the Brabus Rocket 900 Cabrio is going to cost well north of £250,000 once you've optioned it up and imported it to Britain. But, if you aren't put off by that, then you can either pay Brabus direct for a complete car or - if you've already got the current AMG S 65 - you can take it to the tuning house and it will convert it to full Rocket 900 specification at your whim. Prices on application, darling, prices on application...

Matt Robinson - 2 Sep 2017