The first 350 new Minis for the UK's 148 dealers left the Cowley, Oxford, factory last month to go on sale this week. It marked the end of a remarkable 11 months that have seen the former Rover plant completely transformed in order to boost production efficiency.

It is difficult to understand the extent of the transformation just by driving past Cowley – or BMW Group Plant Oxford as it is now known officially.

There is plenty of work still going on, much of it demolishing buildings that have stood for almost 80 years. Faded Pressed Steel signs from the 1930s and ugly 1960s office blocks mask the internal changes.

Inside, the body-in-white and assembly areas resemble the Spartanburg plant in South Carolina, US, where BMW Z3 and X5 are built on a greenfield site that opened in the mid-1990s.

Spartanburg was the benchmark plant for Oxford, said Rainer Bickmann, BMW assembly director, while Regensburg in Germany, where 3 Series is built, was the sister plant. It was, he added, a manufacturing 'twinning' arrangement that allowed best practices to be shared.

More than 200 workers from Oxford spent several months at Spartanburg and Regensburg to become familiar with BMW work practices and production standards.

BMW Oxford now employs 2,500 and is recruiting another 1,800 to add a second shift towards the end of the year. The daunting task of switching production from Longbridge, Birmingham, where Mini was originally to be built, to Oxford began last summer.

Paul Chantry, director of the Oxford bodyshop, said the switch meant moving the £80m Rover 75 production line from Cowley to Longbridge, literally taking the line apart as the last 75 went through the shop, and moving the new £120m production line from Longbridge to Oxford.

That took six months and the first Mini bodyshell was produced in Oxford in January. Ten weeks later, the first fully assembled car was produced.

Mr Chantry said: “The plan was to be producing 85 cars a day by now and we are building 100.”

Full production with a second shift will build 500 cars a day, scheduled for the end of the year. BMW will build about 30,000 Minis this year and 100,000 in 2002.

Herbert Diess, managing director at Oxford, said that even at that low level of production the plant would be globally competitive.

“As with any other product of the BMW Group the new Mini has to and will earn money. Over the life cycle even the first generation of this car will be profitable,” he said. Oxford, highly automated with 229 robots, is big enough to build up to 200,000 cars a year. Other Mini derivatives, including a convertible and a long wheelbase version, are expected to be added to the line-up.

The paint shop was built in 1997 as part of an initial investment of £280m, which includes refurbishing the bodyshop and final assembly areas.

Mr Chantry described parts of the bodyshop, which also produced complete body shells for Rolls Royce from 1949 to the early 1990s, as resembling “a dark, satanic mill”.

BMW has also invested £230m on Mini production facilities, including an innovative rotating cradle that turns the car through 90 degrees to allow easy access to the underfloor. This type of cradle has been used before, but only by low volume manufacturers like Maserati and Ferrari.

The company is claiming a European 'first' with the use of electric power tools on the assembly line rather than compressed air tools, which it says are quieter and more accurate.

Build to order system at Oxford plant

Oxford will become one of the first BMW plants to adopt a new build to order system. Herbert Diess, managing director at the Oxford plant, said: “The target sounds simple – to deliver the cars at the time and in the specification that the customer has defined by online ordering at the dealership.” However, the move meant reorganising the entire production system so that customer orders are allocated after cars have been through the paint shop. This allows customers to alter their orders up to 14 days before delivery, said Mr Diess. BMW claims that working practices at Oxford are among the most flexible in the industry, making the plant highly competitive. At the moment, a single 9.25 hour shift is worked, anywhere from four to seven days a week with the extra days above four being called as late as Wednesday each week. Rainer Bickmann, BMW assembly director, said: “I can do far more here than I could in a German plant.” He added that Oxford would become even more competitive if the UK joined the euro. Everyone is on performance-related pay, with bonuses paid twice a year. Mr Diess said: “We have paid the June bonus and we anticipate paying bonuses in December as well.”