There's no doubt that the new Audi A8 is a technological tour de force; a brilliantly engineered flagship that offers incredible performance, build quality and innovation. By managing to make its brilliant aluminium spaceframe chassis even lighter, Audi has produced a large luxury saloon that's amazingly efficient too. We wish the firm had been a little more daring with its styling, but on the basis of this first drive, BMW, Jaguar and Mercedes should be worried.

MEET the car that Audi says sets the tone for its brand... This is the new A8 – and Auto Express has driven it! The fourth generation of the firm's flagship, deliveries start in May and Audi is hoping it'll be a big hit, beating the BMW 7-Series, Jaguar XJ and Mercedes S-Class in the process.

In the development of the new model, Audi has left no stone unturned. As well as a new body the A8 gets a fresh aluminium spaceframe chassis that's lighter than before, a totally new cabin with a touchpad, infrared nightvision camera and internet access, a revised air suspension system, updated engines, and a new eight-speed automatic gearbox.

So does it feel every inch the range-topper? Well, when you first lay eyes on it, you could be forgiven for feeling a little underwhelmed. Whereas the Jaguar XJ has reinvented itself, the A8 is more of an evolutionary step. However, the more you spend time with it the more its styling subtleties start to grow on you, such as the sharp shoulderlines and beautiful all-LED headlights.

Jump inside and you can't fail to be impressed by the ambience and the space on offer. In comes a wraparound dashboard complete with a gear selector that looks like it's come from a multi-million pound yacht and some gorgeous ambient lighting. Legroom and bootspace are vast while innovation is everywhere too, from the updated MMI system – complete with a touchpad that allows the driver to 'write' his destination into the satnav and boasts a Google search function – to the infrared nightvision system that can spot pedestrians in the dark and help to avoid collisions.

Thanks to an aluminium spaceframe that's some 24 percent lighter than the old car, the new A8 weighs an incredible 200kg less than its rivals. Together with a new eight-speed automatic gearbox and energy recovery, it's remarkably efficient – come September there'll be a 3.0-litre V6 TDI with stop-start that emits just 159g/km of CO2, while even the range-topping 345bhp 4.2-litre V8 TDI diesel we tested emits 199g/km and returns almost 40mpg combined.

With 800Nm of torque it offers phenomenal acceleration too. While the 0-62mph time of just 5.5 seconds is impressive, it's the response from 50mph-70mph – and indeed at much higher speeds – that makes this luxury saloon feel as fast as a supercar. Factor in a super-smooth note that offers barely a whisper on the motorway, and it's clear that this is a deeply impressive all-rounder.

As you might expect, comfort and mile-munching ability are superb. Thanks to a revised air suspension system, the A8 floats along yet feels pleasingly taut at the same time. Only small imperfections like ruts in the road highlight the stiffness of the car's big alloy wheels.

High-spec models like the 4.2 TDI and 4.2 FSI petrol get Audi's active sport differential as standard, and together with Audi's Drive Select system, which allows you to tune throttle response and steering assistance, plus Auto, Comfort and Dynamic modes, the A8 can play sports saloon one moment, cruiser the next.

Backed up by quattro four-wheel drive, grip and security are brilliant – and the only flies in the ointment are the steering, which weights up artificially under load and offers very little feel, and the sheer size of the car, which just can't be disguised. The brakes come in for no criticism though, offering stunning stopping power.

Does the A8 set the right tone for Audi though? Well, it's a subtler prospect than models like the R8 and recent e-tron electric concepts.This is car that hides its considerable light under a bushel. If you want to stand out, you might want to wait for the upcoming A7 – but in the meantime, it should definitely be on your list if you're in the market for a luxury car.