The Land Rover Discovery with top-spec 3.0-litre V6 engine is the pick for big towing jobs, but does that mean the cheaper Discovery with similar 3500kg tow rating but less powerful 2.0-litre four-cylinder turbo-diesel, isn’t up the task? To find out we hitched up a three-tonne caravan to a Land Rover Discovery SD4 HSE and hit the road.