It's facelift time for the Mercedes A-Class. It's the usual stuff: new bumpers, trim changes, better connectivity, lower CO2. Worthy but a bit dull.

More importantly, Merc's also taken the chance to give some far more attention-grabbing tweaks to the A45 AMG.

Can this have anything at all to do with the arrival of the Audi RS 3? The A45 used to be the most powerful small hatchback, and was selling well above its target. And then came the Audi, and so the A45 no longer the most powerful. But now it is again. Because its 2.0-litre turbo, the world's mightiest four-cylinder, mashes out 381bhp.

This isn't just chipping for a boostier turbo either. In fact, max pressure stays the same. Merc has worked on the camshafts and valves among other tweaks.

And that's not all. "For us it's an all-new car," says AMG boss Tobias Moers. Outside he points to the new 19-inch wheels and new front apron. Most of all, though, it's about the performance.

The gear ratios for most of the cogs in the seven-speed dual-clutch box have been lowered. That makes it even more accelerative. Net result is a claimed drop in the 0-100 time from a ballistic 4.6 seconds to a frankly demonic 4.2. From a family five-door hatchback. Sheesh.

With four-wheel drive, getting the A45's power to the road was never a great issue, but, just to be sure, you can now order it with a mechanical limited-slip front differential. That comes in a package called AMG DYNAMIC PLUS. Because shouty capital letters are A GOOD THING.

For that same reason, that package includes AMG RIDE CONTROL. Which is what we humans call adaptive damping. It should make the A45 more useable on lumpy roads.

The exhaust noise, ESP freedom, gearshifts, steering weight, throttle map and damping characteristic can now be controlled through several stages from 'comfort' to 'race'. This system is called, if the TopGear caps lock key hasn't worn out by now, AMG DYNAMIC SELECT.

And the rest of the A-Class range? "We didn't change much of the exterior," says its head of development. Nice that he forgoes the usual crazed exaggeration that car company types use at facelift time.

Anyhow, the current generation A-Class has sold faster than all Jaguars plus all Lexuses in the UK. The world sales are over a million already. So you assume people like the look of it.

Under the skin, adaptive damping is also being offered as an option on the up-spec versions. Mercedes is saying this is an aid to both comfort and handling. Fair enough - with all except the softest suspension and smallest wheels, the current A-Class has a pretty grim ride.

The engines take on Mercedes' new designation, where the petrols have no letter after the numbers, and the diesels are called d instead of CDI. The A180 d SE whiffs out just 89g/km of CO2 in the official test - that's 2.9l/100km - yet makes 0-100 in a not-too-tedious 11.3 sec.

Advanced autonomous braking is standard. On the lengthy tick-box options menu are a bigger central screen that'll connect via Apple CarPlay and Mirrorlink, LED headlamps and radar cruise control. The facelift A-Class goes on sale in autumn.