The reason for the long lead time until we see this go-a-bit-further version of the E-Class Estate is we're only getting the E350d model and it's not been homologated just yet. The rest of Europe gets to enjoy the E220d now, but Mercedes reckons UK buyers won't stomach a £50,000-plus soft-roader with a four-cylinder diesel. So much for downsizing...
Never mind, the E350d All-Terrain will come in a single, top-end specification that will be very similar to the Estate's AMG Line trim. So, that means you'll get the 12.3-inch COMAND screen as standard, sat-nav, heated leather seats, Speedtronic cruise control, Parktronic for those who find such matters tricky, and a powered tailgate.
What you also get over and above the E350d Estate is black plastic cladding around the wheelarches, unique bumpers and grille, and Mercedes' latest 4Matic all-wheel drive system, with adjustable multi-chamber air suspension that's been tuned with mild off-roading in mind.
The knobblier tyres and their taller profile add 14mm to the ride height alone and the All-Terrain's air suspension set-up adds an extra 15mm in normal use, so the ground clearance is 121mm. When the going gets tougher, you can lift the car by as much as 35mm more at speeds of up to 19mph. Above that pace, the car settles back to its normal ride but will also jack up again as the speed drops back below 19mph.
This is all operated through the Dynamic Select's All-Terrain mode and there are further settings for Eco, Comfort, Sport and Individual. The default is Comfort when you fire up the Mercedes and that works just fine in almost every condition.
When you do select the All-Terrain function, not only does it raise the suspension, it also alters the thresholds for the ESP, and traction and yaw controls so the wheels can spin more before any electronic intervention when driving on slippery surfaces. Another element of this setting is the display on the COMAND screen that shows steering angle, incline and the amount of brake or accelerator pedal movement.
This display is hardly vital stuff for a car that's unlikely to venture very far off-road, but the All-Terrain mode proved useful on some icy roads and unmade forest tracks we drove along. You wouldn't have been able to take an Estate on these roads, so this soft-roader model does have an advantage.
It's harder to see what benefits the All-Terrain brings on normal tarmac. You don't get the raised driving position of a GLE and it's no more refined than an E-Class Estate. There's a surfeit of laid back power from the 3.0-litre V6 diesel, which produces 258hp and 457lb ft of torque. That's plenty for overtaking slower traffic and it's all delivered with a refined hum from under the bonnet.
All of that power is sent through a nine-speed automatic gearbox as standard and UK E350d All-Terrains will divide it by sending 31 per cent to the front axle and 69 per cent to the rear, same as the E43 and E63 AMG as it goes. Well, assuming you don't drive the latter in Drift Mode of course. Push the All-Terrain hard through a corner and the front end tracks round until gentle understeer sets in. However, we were driving Euro-spec cars where 45 per cent of power is apportioned to the front wheels, so (in the classic refrain) we'll have to wait to drive a British specification car to know just how the All-Terrain will cope on UK roads.
We'd be surprised if the ride quality wasn't as plush as the cars we drove in Austria. In Comfort setting, the All-Terrain smooches over most bumps without any trouble. Some sharper ridges can be felt, but they don't deflect the Mercedes from its course and are no worse than you'd experience in any other air-sprung SUV or estate. We also tried the E220d All-Terrain and it had a marginally better ride quality and turn-in to bends, but its engine wasn't as quiet when accelerating hard or cruising.
It's a moot point for UK buyers as Mercedes won't be offering the E220d model, which is a shame as it could potentially offer an interesting alternative to Volvo's V90 Cross Country.
This also means we have a wait till Mercedes publishes official performance, economy and emissions figures for the E350d All-Terrain. Given it tips the scales at around 140kg more than the standard E350d wagon, the All-Terrain can be expected to trail its Estate sibling's figures too. This should put the Mercedes soft-roader's numbers somewhere between the Audi A6 Allroad 3.0 TDI and 3.0 BiTDI models.
More importantly, does it put the E350d All-Terrain ahead of the Audi in this small, exclusive class? There's no doubt the Mercedes is just as able to deliver you to your skiing chalet as the Allroad. It also offers more passenger and load space, has a cushier ride and smoother transmission, which is just enough to put the Merc's nose in front.
MERCEDES-BENZ E350D ALL-TERRAIN
Engine: 2,987cc, V6, diesel
Transmission: 9-speed auto, four-wheel drive
Power (hp): 258@3,400rpm
Torque (lb ft): 457@1,600-2,400rpm
0-62mph: 6.5sec (est.)
Top speed: 155mph (est.)
Weight: 2,030kg (est.)
MPG: 50.0 (est.)
CO2: 155g/km (est.)
Price: c. £51,000 (TBC)