Part of the TE Workshop with John Sillence seen here using the Fluke Voltage/Current Meter Calibrator used to calibrate the Avo 8 meters that were very much standard issue in the Directorate at that time.
From Mike Brain
"John spent most, if not all, of his time in the TE section working mostly on the repair of analogue meters. He was very adept at mechanical devices and fitted in very well in the workshop. He of course did calibration of all meters including digital."