2015 BMW 1 Series 125d M Sport first drive

Quite expensive, that's what. This diesel version of the facelifted BMW 1 Series costs almost as much as the flagship M135i. Your £29,800 doesn’t bag you a melodious straight six, either; instead this 125d M Sport packs a 2.0-litre four-cylinder diesel. 

Cylinder count isn’t always everything, however, and this engine is one of BMW’s latest. Its head and block are of weight-reducing aluminium and its specification sheet would satisfy any high-performance engine builder in the land. Forged con rods, a forged steel crank, lightweight pistons and multi-stage turbocharging are among the highlights. The net result is a hefty 221bhp and 332lb ft, sufficient to propel the 125d from 0-62mph in 6.3 seconds. 

You can only get this range-topping diesel with the Sport version of the well-proven eight-speed ZF automatic gearbox, which has been upgraded further. It now looks at the car’s navigation data, even when there’s no planned route, to help select the appropriate gear for the road ahead.

In addition to the new engine and the revisions to the gearbox, there have been some cosmetic updates. Externally, the 1 Series gets restyled bumpers and much sleeker rear light clusters. Inside, you’ll find some new chrome and gloss-black trims, which lift the cabin ambience slightly. Standard kit is adequate and includes single-zone climate control, a DAB radio and the iDrive system with 6.5in screen. As of September, sat-nav will also be standard across the BMW range.

It’s annoying to see that cruise control still remains a cost option, however. When a £20,000 diesel Volkswagen Golf gets adaptive cruise as standard, it’s a bit of a snub to find you’ll have to pay £550 for an upgrade pack to get conventional cruise control in your £30,000 BMW.

Very competent and unquestionably swift, but not especially engaging. This isn't an M135i with a sensible hat on, as you might have hoped. There are obvious similarities, such as the cabin architecture and slick steering, but it lacks its big brother's verve.

In part, this is due to the engine's unexciting sound. You may bemoan the absence of artificially created engine noise but this is one instance where it would be of benefit, since beyond a rising tachometer needle there’s very little to indicate much is going on. That growling, whistling, dump valve-huffing straight six adds masses of character to the M135i, and just a fraction of that is sorely needed in the 125d M Sport. It’s a shame because it can cause you to overlook the otherwise superb four-cylinder engine which is delightfully linear in its delivery, free from lag and eager to reach its redline.

Similarly impressive are the updates to the ZF gearbox. No longer will it simply base its shifts on speed and throttle input; it will now additionally use the car's sat-nav to look at the road ahead and select and hold a suitable ratio until you've dispensed with the oncoming corner. It works well, leaving the car feeling more poised and predictable than it would have done previously. In Sport mode its shifts are remarkably quick, almost to the extent that the transmission does a convincing impression of many a mainstream dual-clutch unit.

It's also quietly gratifying to drive a diesel hatch whose front wheels are freed from transmitting the engine's power to the road. The BMW's steering is consequently uncorrupted, as well as quick to act and precise. However, while the BMW turns in with vigour and, initially, feels like a keen handler, push harder and its lustre dulls a little. For example, catch a mid-corner bump at speed with the rear wheels and you’ll feel a pronounced hop. This slightly unsettling motion cools your enthusiasm a little, and gently persuades you to take a more restrained approach. So driven, it rides and cruises in a very cosseting, relaxed fashion, which is ideal for longer trips.