Leaked: 2021 Mercedes S-Class surfaces

Fresh spy pics of the all-new Mercedes-Benz S-Class limousine have been posted on social media months before we're supposed to see it.

The images that appeared on Spanish car blog,

Almost completely undisguised, save a few stickers and protective wrapping within the cabin, it's clear the Mercedes' latest answer to the BMW 7 Series and Audi A8 will feature a pair of CLS-inspired tail-lights as part of an elegant, if evolutionary, new exterior design.

However, the complete opposite will occur inside seventh-generation W223-series S-Class, which will be the most technically advanced ever and will feature a radical, luxurious and minimalist new interior.

As you can see for the first time here, the big new Mercedes sedan adopts a huge Tesla-style portrait-style infotainment touch-screen that's set to run Benz's next-gen MBUX operating system.

Instead of traditional buttons, smooth touch-capacitive surfaces operate minor functions like climate control.

Blending high-grade materials with the kind of fit and finish once found in significantly more expensive Mercedes-Maybach models, the 2021 S-Class is expected to leap back to the top of its class for cabin design and tech.

Under the bonnet, expect to find a full range of electrified powertrains with even the entry model coming with the car-maker's 48-volt mild-hybrid tech.

The engine line-up will be dominated by either 3.0-litre inline six-cylinder turbo-petrol or 2.9-litre inline-six turbo-diesel mills, depending on the market.

An updated version of Mercedes-AMG's twin-turbocharged 4.0-litre V8 is also expected, but the current model's smooth and powerfulAMG V12 has been pensioned off due to emissions regulations.

From launch in 2021, Benz will also offer full plug-in hybrid versions of the W223. There's no official confirmation, but it's thought larger lithium-ion batteries should ensure that the large hybrid limo should be capable of covering at least 100km on pure-electric power alone.

Both rear-wheel drive and all-wheel drive will again be offered.

What will be lacking is a pure-electric version to challenge the upcoming battery-powered Jaguar XJ.

That's because the S-Class has been developed alongside the Mercedes-Benz EQS -- a large four-door flagship four-door 'coupe' that sits on the car-maker's dedicated MEA (modular electric architecture) platform.

Both models will introduce Mercedes-Benz's latest autonomous driving aids, including a Level 3 highway assist function that will drive the car itself but only when permitted by GPS mapping and road conditions.

The next S-Class will remain based on (a heavily updated version of) Daimler's Modular Rear-wheel drive Architecture (MRA) platform, which should bring weight-savings over its W222 predecessor.

Powered by a new 48-volt electrical architecture, new technologies will include next-gen AirMatic+ active suspension, which uses cameras to scan the road surface and pre-arm the air suspension and dampers for bumps ahead.

New active anti-roll bars will also ensure flat cornering, even at very high speed.

Unlike the model it replaces, it's rumoured that Mercedes will only produce a long-wheelbase version of the new S-Class, which could see the W223 measure in at an imposing 5.3 metres long.

The new Mercedes-Benz S-Class is set to be launched in Europe this September, before first deliveries begin before the end of the year, followed by an Australian release in early 2021.