The new generation of Minis to be powered by engines built at BMW's Hams Hall plant near Birmingham was unveiled last night.
The arrival of the new Mini Cooper and Cooper S models later this year will complete the Munich group's British "manufacturing triangle".
Hams Hall's engines and body panels from Swindon will converge on BMW Plant Oxford for assembly.
The triangle is "one of the true automotive UK success stories of recent years", BMW said.
The new cars, to be followed by a second generation basic Mini One model in 2007, will see production levels at Oxford - which has had a £100 million upgrade this year - to the 240,000 a year mark.
Hams Hall, which represents an investment of more than £400 million by BMW, has added Mini's 1.6 litre engine, developed jointly with PSA Peugeot Citroen to the range of four cylinder petrol engines it already supplies to plants in Germany, the US and South Africa.
The plant's workforce has been expanded by half to about 975 to cope with the extra work.
Mini has been a runaway success for BMW since the new version of the marque was launched in 2001 with total global sales of more than 800,000, twice the original anticipated volume.
The new cars have new interiors and with subtle changes to the exterior. They will be greener and more economical to run, the company claims.
The £12,995 Mini Cooper will be able to accelerate from 0-62mph in 9.1 seconds and will have a top speed of 126mph.
The Mini Cooper S, costing £15,995, will reach 62 mph in 7.1 seconds and will be capable of speeds of up to 140 mph.
The Mini Cooper's fuel consumption will improve from the present 40.9 miles to the gallon to 48.7 mpg, while the Mini Cooper S will improve from 32.8 mpg to 40.9 mpg. Twelve body colours will be available.