Mercedes GLA 220 CDI 4MATIC AMG

It had felt like entering the lair of a Bond villain as I crossed the footbridge over the River Calder and entered the angular grey building to hear how the luxury German marque planned to attack the mainstream small-car market head-on.

The only difference was that I would be greeted by a bacon sandwich and a cup of coffee, not an early bath in a pool filled with hungry sharks.

Since then the A-Class’s handsome styling has seen it attract more than 50 per cent of its owners from rival brands and the foundation stones it laid have spawned a four-door coupe and now this, the GLA SUV.

Billed as a baby brother to the ML, GL and monstrous G-Class, it is some 125mm longer, 24mm wider and 61mm taller than the A-Class and boasts a 70 litres larger boot (412 to 341 litres).

Following the lead of various soft-roader SUVs, the GLA is available in front-wheel-drive guise or with Mercedes’ 4MATIC system, commanding a premium of £1,915.

The GLA 220 CDI 4MATIC AMG Line tested here came in at £31,030 as standard and £33,275 after metallic paint, the Park Assist automated parking system, an uprated Becker sat-nav and Mercedes’ trick new Drive Kit Plus for iPhone 5 were added — pitching it a couple of thousand pounds cheaper than BMW’s incongruous-looking X1 xDrive25d M Sport.

In terms of power, the BMW betters the Mercedes with 218bhp and 332lb.ft. of torque beating 170bhp and 258lb.ft.

Accordingly, the GLA lags behind in terms of acceleration, its 8.3-second sprint to 62mph well short of the BMW’s 6.8 seconds.

Mercedes has been chasing efficiency scores as of late, though, and makes much of the GLA’s 0.29Cd aerodynamic drag score.

This, coupled to regenerative braking, a reasonable 1,535kg kerb weight, stop/start technology and the fuel-saving efforts of the 7G-DCT gearbox (more on which later) makes it the winner in terms of efficiency — blitzing the BMW with its 55.4mpg and 132g/km CO2 score (versus 47.9mpg and 154g/km).

In terms of in-the-metal appeal, the GLA may split opinion according to the angle from which it is approached. The front end is larger, with bigger features than its hatchback sibling and an over-sized grille and Mercedes badge making it appear like an A-Class overdosed on botox treatments.

Even at 18 inches, the wheels looked a little overawed by its larger structure.

At the rear, things are far better resolved, with a broad, squat appearance, silver diffuser and twin exhausts. From no angle does the GLA seem particularly tall. Roof rails, a sump guard and hill descent control all allude to off-road abilities, but ground clearance is fairly minimal.

There is a premium feel from the off, a theme continued inside with the youthful interior of the A-Class hatchback.

That 5.8-inch, tablet-style infotainment screen may look like something of an afterthought but this is one of my favourite cabins.

Five satin-effect cross-hair air vents take prominence, with silver brightwork picking out door handles, pedals and the main part of the dash.

In the AMG Line, red stitching sets off the leather seats and a chunky sports steering wheel.

Silver speed and rev dials are not easily read but a crisp TFT screen between them offers a far more legible speed readout.

The three rear seats echo the sporty items in the front — strongly side-bolstered in their design — but head and legroom feels no better than in the A-Class and a high shoulder-line lets little light into the cabin.

The AMG Line’s sports suspension is 15mm lower than standard and feels firm, occasionally fidgety.

In terms of body control, it serves the driver well, but passengers might be surprised by the relative lack of comfort.

Mercedes’ 2.1-litre turbodiesel engine is not the most refined, but pulls well and returns impressive economy if you drive to the strengths of the 7G-DCT automatic gearbox.

But too often I found myself infuriated by its tardy shifts and hesitation at junctions.

Many times, I stopped short of going for gaps in the traffic as the gearbox searched for a ratio.

Similarly, such was its desire to stick in a high gear to save fuel that I soon adapted my driving style, flicking in down-shifts via the steering wheel-mounted shifters on the approach to a corner to avoid coasting unnervingly round.

In terms of style, economy, technology and premium appeal, the GLA has it licked.

But the AMG Line failed to satisfy in terms of comfort or dynamic performance during my test and I was left feeling that customers moving up from the A-Class might crave more space.

Just as the A-Class moved well away from its MPV forebear for its rebirth in 2012, I cannot help thinking that Mercedes’ compact SUV should be a little further removed from the hatchback in creating the GLA.