That could be it but normally the indicator for a RHC was horizontal in the signals square, especially in the 50s/60s
The convention was 'When in the ATZ, all turns are to made to the left' for which there was no signal but there should have been a signal in the signals square showing a right angled board covered in white and red stripes which would indicate 'RH circuit in force'.
Could the photos above be Pendeford by any chance?