David Jolley - Automotive News Europe November 12, 2015 06:01 CET FRANKFURT -- BMW Group's Dutch contract manufacturing partner has started making the new Mini Convertible. Production of the softtop model began at VDL NedCar on Nov. 1 ahead of the convertible's sales launch in March, a BMW spokeswoman said, declining to detail how many vehicles will be built annually at the plant in Born, Netherlands. BMW has already transferred some output of its Mini hatchback models to VDL NedCar to ease capacity constraints at Mini's sole production factory in Oxford, England. Previous generations of the convertible were built in Oxford. The new Mini Convertible is one of five core models Mini is retaining as the brand moves to focus on volume cars rather than expand into more niches. Alongside the convertible, the brand will keep the three- and five-door Mini Hatchback, the Clubman and the Countryman. Mini's global sales fell by 0.9 percent to 302,183 vehicles last year. Of these, 17,327 were convertibles. The plant was previously owned by Mitsubishi, which built the Colt subcompact and the Outlander SUV there. After ending production at NedCar in 2012, Mitsubishi sold the plant to local bus maker VDL Groep for 1 euro.