Having just re-discovered my copy of the original script I can confirm it is Lord Londonderry, who was a major land and coal owner in the North East at the back end of the 1800s. (this is the script for the 1968 performance which according to the notes was at "The Flora Robson Playhouse" in Jesmond not the Peoples Theatre which is further along the same road. The cast included Bryan Pringle, John Woodvine and Colin Douglas. oh yes and in a minor role as one of the "Village Children" yours truly *modest blush*)