The makers of Dr Martens shoes, R Griggs, announced on Friday that they are to close six of their ten factories. Griggs has estimated the job losses to be in the region of up to 350, out of a total workforce of 2,450. The changes are to allow the company to alter its working practices, introducing 'cellular' manufacturing based around small groups of personnel each carrying out a variety of jobs.The six closures are all in Northamptonshire, leaving two factories in that county, one in Leicestershire and one in Somerset.Griggs claimed: "In a very competitive marketplace, prospects for the brand remain healthy," but that following a comprehensive review of manufacturing processes, the company is unable to transfer production from traditional track methods to modern practices, working in teams. This method requires less space and less people.The factories destined for closure are based in Wollaston, Kettering, Irchester, Irthlingborough and Finedon.