186g/km-plus (tax bands J-M): Mercedes ML

It's been a couple of years since a Mercedes graced the podium in this competition. So it’s a welcome return for the brand, with the ML350 BlueTEC Sport.

The field in this high-CO2 category was the smallest this year, with only three entrants. And the M-Class easily came away with the trophy.

It certainly looks the part, with its sturdy stance and high driving position, but looks aren’t enough for the discerning tow car buyer. So how did the revised V6 fare once hooked up to the top-spec Bailey caravan – the impressive Unicorn Barcelona?

Put simply, the big SUV was outstanding. The engine sounds great, and it hauled the Unicorn around our test routes easily and with surprising poise and agility. The seven-speed auto made the best of the V6’s torque, and it coped well with steep inclines.

Cruising at 70mph posed no problems, and with 620Nm of torque the ML pulled itself and the caravan from 30-50mph in just 5.8 seconds. Plus, you get to enjoy this effortless performance while sitting in comfortable leather seats, surrounded by loads of hi-tech kit in the cabin.

But you’ll need deep pockets – the ML costs nearly £50,000, while our test car had £20k of extras fitted. Emissions of 189g/km mean road tax is a steep £250 a year, too, although claimed economy of 39.2mpg is good.

Our finalists

Mercedes ML350 BlueTEC Sport: £49,440Ford Ranger Wildtrak: £31,723Isuzu D-Max Eiger 2.5: £21,275*

* On-the-road price without towing extras.