After the flotation of Northern Ireland Electricity on the London stock exchange in 1993, Winsor was seconded to the Government Legal Service. He served as chief legal adviser and general counsel to the first Rail Regulator, John Swift QC. The Rail Regulator was the statutory officer established by the Railways Act 1993 for the economic regulation of the British railway industry, which was about to be privatised. Winsor's secondment lasted two years and he returned to Denton Hall in August 1995.