Mercedes’ particular mechanical specification for the E400 puts the car on low-profile run-flat tyres and air suspension as standard (whereas its less powerful range mates can be had with steel coil springs if you prefer).

This is something of a regrettable combination because run-flats tend to introduce a little bit of harshness into any car’s ride compromise on account of their necessarily stiff sidewalls – and since air suspension is ill-suited to the dampening of that harshness, the chassis’s solution to the typical UK B-road dilemma can seem ungainly.

Matt Saunders Autocar

Matt Saunders

Road test editor
It takes its time to settle on the turn-in to tighter bends. The handling balance lacks front-end bite

Curiously, it is in Comfort mode where the mis-match tends to irk most. The coupé’s softest setting is well-meaning enough and its syrupy pitch and heave are obviously intended to keep you at an E-Class-sized distance from the road surface. But it only works on motorways and the smoothest of A-roads.

Away from them, rather too obviously and often, the experience of the suppleness is thwarted by obstacles too tall, deep or sharp for the suspension to mitigate before gracelessly registering with the occupants above.

Better instead to drive in Sport mode, where the impression of a fast modern pseudo-performance coupé becomes far more consistent. True enough, the bristling response to B-road abnormalities remains, except now it occurs against the background of a much more closely damped attitude to body control. As well as making the coupé more purposeful, the difference causes a generous resetting of driver attitude, making the secondary infractions forgivable in the light of a sportier bent.

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Ultimately, though, it does not elevate the model far above adequacy and nor does it deliver the sophisticated compromise of a properly sorted GT car. At normal road speeds, the E400 corners with decent grip, handling with respectable steering response and directional precision.

Press the car hard, though, and you’ll find it is quite willing to make its front tyres squeal before you’ve put them under much duress and it lacks the on-limit balance of some of its competitors.

But then you don’t expect handling brilliance here: for us, it’s the E400’s lack of ride sophistication that dulls what we’d expect to be the car’s cutting edge.

The E400 isn’t a car that responds well to being driven to extremes. It copes, and it can be driven fairly quickly, but it doesn’t take much provocation to plumb the depths of its reserves.

The car seems particularly keen to overwork its front tyres during hard cornering. Your speed needs to be only moderately high before the front tyres begin their howls of complaint, although the onset of noise comes much earlier than the ultimate exhaustion of grip.

The E400 resists roll quite well, but it takes a while to settle on its outside wheels and can seem a bit reluctant to turn in. It’s better mid-corner, although you need to saturate the front tyres with torque before the four-wheel drive system diverts torque away from them to the rear.

The power of the brakes also seemed slightly limited during our testing. It was a little too easy to trigger the ABS during urgent high-speed stops.

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