As good as the six-cylinder diesel engine fitted to the Range Rover Td6 was, it was difficult to hide the suspicion that this unit was punching above its weight. While it was a great engine for cars the size of a Jaguar S-TYPE or, indeed, a Peugeot 407, expecting it to power a Range Rover against the likes of the Volkswagen Touareg V10 TDI was asking a bit much. The Volkswagen skewed the market in terms of what we expect our big diesel 4x4s to do and Range Rover has responded with the TDV8, a diesel engine that's good for 272bhp.

Leaving aside the freakish Volkswagen for a moment, this power output is enough to put clear air between Range Rover and the top diesel engines fitted to luxury 4x4 models from Mercedes (221bhp), BMW (218bhp) and Audi (230bhp). It's also an engine that's more befitting of a vehicle that needs a truly imperious powerplant. Range Rovers don't do 'average' or 'run of the mill' at all well. The brand positioning dictates that a Range Rover should be the top of the tree and a 188bhp diesel just didn't offer that sort of kudos.

Eight cylinders are always a good start and the Range Rover makes the most of its octet of oil-squashing pots. It's more than just the old six cylinder plus two. Compared with the outgoing engine, it's 54 per cent more powerful, delivers 64 per cent more torque but, crucially, offers similar fuel economy. As you'd expect with that sort of power gain, acceleration is vastly improved, slashing the sprint to 60mph to 8.5 seconds and giving a top speed capability of 124mph - easily enough for high-speed intercontinental ballistic cruising. Refinement has been improved too. The TDV8 is claimed to be 75 per cent quieter overall and you won't need to rev it until its valves bounce because the almost obscene torque figure of 472lb/ft comes on stream from just 2,000rpm. Almost two thirds of that figure is on tap from just 1,250rpm, which is more than the old engine could make at full chat.

"Progress usually comes in small incremental nibbles. The Range Rover TDV8 has taken a Great White sized bite out of the opposition here"

This means that acceleration feels effortless. The 12.7 second sprint to 60mph of the old car was a bit embarrassing and the midrange performance has been transformed. The engine exceeds Euro4 emissions standards and a combined fuel economy figure of 25.3mpg is a decent return for such a sizeable and swift hunk of automotive real estate. Many will labour under the misapprehension that this powerplant is the TDV6 with a couple of extra cylinders grafted onto the end but it's far from it. Whereas the six-cylinder V6 had a bank angle of 60 degrees between the two sets of cylinders, the V8 has a 90-degree angle which is often regarded as the most efficient configuration of an eight-cylinder engine's balance and refinement. Displacing 3.6-litres, the TDV8 uses a revolutionary Compacted Graphite Iron (CGI) engine block that offers better fatigue strength than aluminium with less weight than a 'standard grey' iron casting.

So confident are Land Rover that they can virtually match the refinement of a petrol engine that they've felt the need to develop a patented device for the Range Rover TDV8's fuel filler neck, to avoid the risk of inadvertently fuelling from the green pump. A glass-reinforced nylon engine cover and sound-deadening rubber covers wrapping the fuel injectors mute the high-frequency thrash that often comes from powerful diesel engines.

This being a latest model year Range Rover, you also get a number of added technologies and interior tweaks. New gadgets include Land Rover's superb 'Terrain Response' system that makes this car even easier to use in the unlikely event that you venture off road. There's also an electronic park brake and an electronic rear 'e' differential. The improved cabin meanwhile. gets extra stowage space, enhanced finishes and more effective air conditioning - plus the option of cooled front seats.

If you're used to older versions of this current shape Range Rover, you'll also notice that at the wheel of this new one, the steering has been tweaked for better feel and the air suspension has been revised to offer better on-road comfort and off-road performance. The interior is, as we've suggested, a major selling point of this vehicle. Jet/jet is an all-black colour scheme that works wonderfully with black leather and black metallic paint whereas ivory/jet lightens the tone a little and looks good with classic green, blue and red exterior finishes. As well as being faster, the Range Rover is also quieter than before, all engines doing better in terms of noise, vibration and harshness than their predecessors. Notwithstanding this fact, Land Rover have also isolated the engines from the interior more effectively. The front side glass is now laminated to cut down on noise and the A-pillar has been reprofiled to reduce wind roar at high speed.

A wide range of electronic functions is available, including a rear camera for easier reverse parking, a tyre pressure monitoring system and adaptive front headlamps that swivel when cornering to improve illumination. A rear seat entertainment system is also on offer, with two headrest-mounted 6.5-inch screens, a six-disc DVD auto-changer, infra-red remote control, wireless headphones and sockets for auxiliary media sources (such as an MP3 player or games console). The latest models also benefit from an electronic park brake, more effective four-zone air conditioning - plus the option of cooled front seats. There's also a 'climate control' windscreen and side glass, available in conjunction with automatic rain and light sensing.

Other luxury appointments include a DVD satellite navigation system that provides both on and off-road guidance, a Logic 7 harman/kardon audio system boasting 14 speakers with 710 watts of power, and a personal integrated telephone system. This latest in-car phone is Bluetooth-enabled and can be voice, touch-screen or steering wheel operated. Cradle-mounted phone handsets also allow for SMS text messaging (via an on-screen keyboard). A touch-screen is standard on all models. It has clear resolution for easy visibility in all light and provides an interface for audio, navigation, on-board computer, telephone, and 4x4 information and settings. It's impressive stuff.

Land Rover started its wholesale refurbishment of its range with the Discovery and now the Range Rover and Freelander are getting into step. The TDV8 is just one small step in the relentless march towards total 4x4 domination. You can't forestall inevitability.