2015 Mercedes-Benz GLC 350 e 4Matic first drive

What it might have been is one of the most interesting versions of Mercedes’ latest SUV. It may even still prove to be, in a few years' time. This, then, is the GLC 350 e, the company’s petrol-electric plug-in hybrid alternative to the usual mid-sized, five-seat family 4x4.

Like its diesel siblings, this one has got full-time four-wheel drive and height-adjustable air suspension. But unlike them it offers the potential to combine a sub-six-second 0-62mph sprint with a fleet-friendly CO2 emissions rating.

Well, it’ll offer those things in markets where you can actually buy it. While the other versions of the new GLC use Mercedes’ new nine-speed automatic transmission, the 350 e can only currently work with the old 7G-Tronic-Plus torque converter gearbox also used in the S 500 plug-in hybrid. Without splashing out on an expensive re-engineering program, Mercedes can’t make that gearbox fit a right-hand-drive car with four driven wheels. Sound familiar? That’s probably because it was precisely those RHD conversion problems that kept the GLC’s predecessor, the GLK, from going on sale in the UK.

Mercedes is working on a nine-speed PHEV powertrain to address the problem, so there is at least some far-off hope for UK customers interested in the GLC 350 e. So with a plug-in hybrid Porsche Cayenne already on the market and rivals from BMW and Audi imminent, is this Mercedes a good reason to keep your money in your pocket for now?

Disappointing in one respect. A 300bhp pseudo-performance SUV really ought to be more tantalising and enjoyable to drive than this.

The GLC 350 e, like all of Mercedes’ hybrid models to date, is the sort of car that’s at its best when driven unhurriedly. On more modest accelerator pedal openings, the electric motor copes well with the car’s two-tonne bulk. You’ll keep up with urban traffic easily, and maintain an A-road cruise without trouble.

But when you stretch the powertrain with wider throttle applications, the sheen comes off its style of delivery. Ask for full power and there’s often an unflattering delay before the combustion engine can wake up and supply it, followed by an unseemly lunge. Performance is strong in outright terms and powertrain response is better when the car is bowling along at more consistent speeds. But in manual mode, gearchanges can sometimes take a split-second longer than they should.

Brake pedal feel, a perennial bugbear of hybrid-electric cars that regenerate kinetic energy before activating their friction brakes, is also poor. Braking power ramps up suddenly beyond a certain point, and smooth progress can be tricky at low speed.

For keener drivers at least, other manufacturers offer more satisfying plug-in hybrid powertrains. But Mercedes may not worry too much about that, given that GLC owners will be used to making similar dynamic sacrifices relative to more agile-handling SUVs such as the Land Rover Discovery Sport and BMW X3. And given that the GLC 350 e, also like its rangemates, has strong practicality, commendable mechanical refinement and a fairly laid-back, cushioned ride to act as selling points.

The GLC’s high-voltage electric propulsion system is in effect noiseless from the driver’s seat. It’s powerful enough that you can quite easily keep the combustion engine from starting around town while comfortably keeping up with the traffic.