Top speed: 155mph (limited)
Economy: 37.7mpg combined
Engine: 6-cyls, in-line, 2979cc, petrol turbo
Power: 316bhp at 5800rpm
Torque: 332lb ft at 1300-4500rpm (with overboost)
Gearbox: 8-spd automatic
A mix of dry and damp, tight bends and a narrow road should be challenge enough for a hot hatch with 316bhp to spill from its rear wheels. And if that sounds like a temptingly reckless number then you'd be right it's only 19bhp down on the output of the lately departed 1M Coupe, and the M135i's 320lb ft of torque is identical.
Either way, this new three-door 1-series is eagerly, muscularly and excitingly quick with the potential, you may think, to become a flailing handful if you dare to meddle with the ESP button. But the first bold dive into a rain-sheened bend uncovers grip reserves far deeper than expected deep enough that when that DSC button is prodded for partial disengagement, it takes some lead-foot ambition to get the rear axle's wider 245/35 R18s to get a skate on, the slide part-managed by a brake-deploying virtual limited slip diff.
So it's pretty neat, controllable and reassuring, the more so because this rear-driver is quite a finely balanced tool, as proved by a too-fast arrival into a tight, low speed turn that fails to bring on any plough-on understeer. That said, you can expect to see plenty of the orange light that confirms an active ESP system, which is no surprise given all this energy and rear-wheel drive.
The result is a an excitingly rapid drive that sits just the right side of hectic, the excitement of the six's keen blare built on by the 'box's light thumps in sport, the ra-ta-tat of the exhaust's over-run, the lightly clasping support of the seats and an excellent driving position. While some may desire the more uncompromising character of the 1M Coupe, the fact is that this M135i's ride is less maskingly firm, its steering more delicate and its character easier to live with. And it's also a whole lot cheaper, being almost £10k less.
More immediately noticeable M135i identifiers include a new front bumper unit with larger air intakes, a rear bumper with twin exhausts and 18in alloys, and tyres, that are wider at the rear. Inside you get leather sports seats (the UK won't be getting the appealing Alcantara/hexagon cloth mix of the test car, which seems a pity), a black headlining, an M footrest, blue accent stitching to the seats, patterned aluminium trim inserts and modified instrument faces. Not a huge amount of differentiation then, but enough to mark this 1 out as something sportier. The cabin is robustly constructed too, although it's not as finely, designed, finished or textured as the cabin of the latest Audi A3.
Throttle response is not as instant as you'll find in a normally aspirated M3, but it's sharp enough for most circumstances. Couple the six's breadth of urge to that eight-speeder, and you have a car that powers near seamlessly from a dawdle to its easily struck and restricted - 155mph maximum.
M division has tuned the 135i's exhaust to provide a smoothly busy soundtrack that makes paddling your way through eight ratios an absorbing business, even if the noise can turn slightly wearing. Happily it quietens off at a motorway cruise. And we suspect the same may be true of the ride, which showed signs of choppiness on Germany's mostly smooth roads.
by Richard Bremner