Most body panels are shared with the 1 Series 5dr, but there are longer front doors, frameless windows and a slightly different side window profile. Compared with the outgoing 1 Series 3dr model the new car is 8.5cm longer; BMW claims a 2.1cm improvement in rear legroom.
The new 1 Series 3dr will be a rival for cars such as the new Audi A3 and Volkswagen Golf 3dr. Itll also compete with the forthcoming three-door version of the new Mercedes A-Class, which is due in 2013.
Most of the engines available are familiar from the current BMW 1 Series line-up, but there are new additions at the top and bottom of the range. The entry-level model is the 114i, which has a 1.6-litre four-cylinder petrol engine that develops 101bhp. Average fuel economy is 51.4mpg and CO2 emissions are 129g/km.
The M135i has a turbocharged 316bhp six-cylinder engine and BMW quotes an official 0-62mph time of 5.1 seconds (4.9 seconds for the automatic version). It gets bespoke suspension and steering settings, and a range of cosmetic upgrades, including sportier bumpers and 18-inch alloy wheels.
Prices for the BMW 1 Series 3dr start at 17,830 for the 114i ES and rise to 29,995 for the M135i. First customer deliveries are expected in September.