It’s a feat achieved by re-mapping the engine to increase boost pressure and stretching the rev limiter by 200rpm. To cope with the extra stress there’s been some beefing-up of the internals, including stronger head gaskets and modified exhaust valves.
Fundamentally the drivetrain remains the same. The engine’s mighty output is distributed to all four wheels through an eight-speed Tiptronic automatic gearbox. From there, and under normal circumstances, a central differential sends 40 percent of the drive to the front axle and 60 percent to the rear - where it’s divided once more by an electronic limited-slip diff. But, if needs be, up to 100 percent of the drive can go to the rear.
As the standard S8 has been known to cook its brakes when driven hard, we'd opt for the Dynamic Pack. It includes fade-resisting 19in carbon-ceramic brake discs and swaps the 155mph limiter for one that pegs things at 189mph instead.
The result is brutal acceleration accompanied by a gloriously deep baritone rumble from the quad tailpipes – which for S8 Plus spotters, are painted black instead of the standard car's chrome.
One Audi engineer told me this car should crack 200mph with no restrictor, and they’d only limited it because of the tyres - or perhaps to spare the blushes of the Bentley Flying Spur? Judging by the phenomenal rate at which the S8 Plus keeps pulling, even when it’s already at mammoth speeds on a de-restricted autobahn, I feel no reason to doubt the claim.
In these situations Dynamic mode works best. It stiffens the suspension and helps keep the big Audi planted even as you motor past trundling HGVs. It also weights up the Dynamic Steering, which otherwise feels a bit insubstantial, albeit quick.
The test route didn’t take in many twisty roads, but preliminary analysis indicates that for its size, the S8 is pretty wieldy. Traction is epic and it manages to resist rolling much on its uprated air springs, even as you pile on more cornering speeds and lateral g.
However, all this agility isn’t at the expense of the S8’s other role as a cosseting chariot for the well-heeled. Yes, it has smoother-riding peers, but switch to the softer Comfort mode and it floats along without much fuss, even on the standard 21in rims.
Whether it’s because of the trick noise-cancelling software or layers of old-school sound deadening, the road and wind noise never startle, even at very startling three-figure speeds.
If you’ve had a particularly stressful day, you can ensconce yourself in the big, quilted leather seats with contrasting red piping and stitching. You may choose to unwind further with the massage feature, or maybe fire-up the Bang & Olufsen stereo, both of which are on the options list. Whatever your pleasure, you can bask in the glory of one of the most solidly built interiors that money can buy.
As for the standard equipment front the S8 is certainly well-equipped as you would expect on a £80,000 car. The 'entry-level' S8 gets all the equipment found on the SE Executive trimmed A8s and adds 20in alloy wheels, Audi Sport tweaked air suspension, electronic differential and steering, along with LED headlights and 360 degree camera on the outside, while inside there is a Bose sound system fitted, a CD/DVD player, acoustic glazing, a Valcona leather upholstery and 22-way electrically adjustable front seats.