These drawings appear to be by Crown House Engineering Ltd, but they also contain Theatre Projects Consultants Ltd information in the details box. They divided them into the following series:
904/201-300 - Lighting Installation
904/701-800 Electrical Installation
904/7101-7200 Electrical Layout Plans for Olivier and Lyttelton Theatres
All drawings are marked with an 'R' at the end of their reference numbers to show that they are 'record' drawings.