Few photographs remain of the three Claytons claimed after withdrawal by the Research Centre at Derby. D8521, seen here, was the subject of a project to convert the locomotive to a mobile generator and gained various conduits and cables above one of its bonnets. Its useful purpose served, it then languished parked at Mickleover, the centres test line. During the machines time under experimentation it was renumbered twice, 18521 before finally becoming S18521. Also of note in this photograph is one of the Research Centres other ex-BR machines, Class 23 'Baby Deltic' No. D5901.