MERCEDES-BENZ GLC 300DE

Does a plug-in hybrid make even more sense when it's diesel-engined?

- JAMES DISDALE

To the surprise of nobody, Mercedes' medium-size SUV has been one of its best-sellers ever since its 2016 launch. Part of the GLC's success is down to its wide variety of hybrid powertrains, from mild to plug-in - and intriguingly, this uniquely includes a diesel PHEV, the 300de, which we're belatedly driving for the first time here.

This combination of compression ignition and electricity seems a slightly confused offering. On the one hand, it's a heavily electrified PHEV with an official electric range of up to 78 miles, which makes it very tempting for company car drivers. On the other hand, it's that four-wheeled bete noire, a diesel.

However, you could argue that it really does represent the best of both worlds. For most of your daily chores, it runs in smooth, efficient, zero-emissions EV mode. When you want to go farther, no powertrain offers such excellent long-distance efficiency as a diesel. So, does the theory work in practice?