Mr S R Devlin retired from the company in 1965. After a number of changes of ownership at higher levels, during which time Clayton Equipment Ltd established itself as a market leader in underground rail haulage solutions. International Combustion was acquired by Clarke Chapman Ltd of Gateshead in 1974 and in 1979 the organisation merged with Reyroll Parsons of Newcastle, manufacturer of large steam turbines for power stations, etc., to form a new company called Northern Engineering Industries which at one stage employed in the region of 35,000 people. Ten years later, Northern Engineering Industries (NEI) was acquired by Rolls-Royce as part of a strategy to diversify its product line into industrial power, and Clayton Equipment became a part of the Rolls-Royce Industrial Power Group in 1989. In 1994 Rolls-Royce divested itself of the remaining companies within the Northern Engineering Industries Mining Equipment Group, retaining only Clayton Equipment. Consequently, the company was put under the control of Rolls-Royce Materials Handling based at Gateshead and then later Rolls-Royce Industrial Businesses in Derby. It nonetheless retained a significant measure of autonomy, and in March 2005, it became an independent company again.