The 500,000th MINI is a dark silver Cooper S, whose American owner was invited across for the occasion. Around three-quarters of all MINIs built so far have been for export, and it's a remarkable statistic that MINI is now the UK's fifth biggest car manufacturer.

Britain's secretary of state for work and pensions, Andrew Smith, was at the plant to wave off the car, a dark silver Mini Cooper S bound for the US - the car's the second-biggest market after the UK.

"This is a great moment for the workforce and British manufacturing," Smith said. "The Mini plant is a success story that is benefiting both the local and national economy."

The Half-Millionth MINI was delivered in England to Dan Cowdry of California, who said: "It's a real treat to see the home of MINI in Oxford but I'm really looking forward to showing the car to my friends back home."

The MINI is the smallest car on the road in the USA but, since its launch early in 2002, nearly 80,000 have been delivered.

Cautious initial forecasts by the company predicted that the plant would build 100,000 MINIs a year but worldwide demand brought the half-million milestone forward by two years.

More than 176,000 MINIs were sold in 2003 in 70 countries from Thailand to Trinidad, but 2004 looks like it will be setting another record with 111,142 sold in the first seven months of the year – four percent more than the same period in 2003.