Engine options, top speed, acceleration and refinement

All three diesel engines available in the BMW 1 Series hatchback use the same 2.0-litre common-rail unit found in other BMWs. The base 116d has 115bhp, the mid-range 118d has 143bhp and the range-topping 120d 181bhp.

Confusingly, the 125d also features a 2.0-litre powerplant, but of a newer design and shared with the X1. It produces 215bhp, 332lb ft and, when equipped with the eight-speed auto, a remarkable 126g/km of CO2 and 58.9mpg.Even the 120d offers more than adequate performance; with 280lb ft of torque from 1750rpm, 60mph comes up in around seven seconds.

The engine's generous mid-range torque allows it to accelerate out of corners with the urgency of a middle-order hot hatch

With 280lb ft of torque from 1750rpm, performance from the 120d is as strong as you’d hope: 60mph comes up in around seven seconds. The powertrain’s all the more exceptional because, fitted with ZF’s excellent eight-speed automatic gearbox as an option and BMW’s Efficient Dynamics fuel-saving ancillaries as standard, the car emits less than 120g/km of CO2. This vehicle is capable of bettering both 140mph and 60mpg; not at the same time, of course, but remarkable from the same car.

The 143bhp 118d takes 8.9sec to cover 0-62mph whereas the 120d manages it in 7.2sec. Perhaps most impressive of all is the fact that the most powerful version of the engine emits only 2g/km more than the 118d’s 118g/km and is quoted as having the same 62.8mpg combined fuel consumption as the lower-powered car.

The choice between the 118d and its more powerful brother is going to come down to money because, in the real world, the difference in performance is not wide enough to count.

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Three petrol versions of the five-door are also offered: the 218bhp 125i is now offered alongside the 167bhp 118i and the entry-level 134bhp 116i. The latter two are powered by a 1.6-litre engine that, BMW says, is its first petrol four-pot to feature twin-scroll turbocharging, direct injection, Valvetronic variable valve timing and double-Vanos variable valve lift. Even in base 116i form, it’s an impressive motor on paper, producing 162lb ft of torque from 1350rpm and an almost diesel-rivalling 177lb ft on overboost.

The twin-scroll 2.0-litre turbocharged engine in the 125i develops 228lb ft of torque to accompany the 218bhp produced, and enables the 125i to hit 60mph from rest in 6.5 seconds and record a top speed of 151mph.

The BMW M135i sits at the top of the 1 Series range. Despite being a half-way house M Performance model, it delivers performance that matches that of the fully-fledged 1 Series M Coupe. When specced with the automatic gearbox, the M135i can sprint from 0-60mph in under five seconds and reach a limited top speed of 155mph. Lag is minimal from the turbocharged three-litre straight-six, and stunnng performance is available throughout the rev range.