The 'Sticky-Back Plastic' or 'Scotchal Fluatape' was first trialled in 1961 following problems with the previous 'Fluolac' fluorescent paint on Flying Training Command aircraft, which tended to quickly peel from the airframe. I believe that RAF Cranwell experimented with several designs with the tape because of the position of the College's 'Ring of Confidence' on the rear fuselage until the definitive design was approved
BTW: Ken Parry: that is superb image of a 3 FTS JP, which must have been taken the year after the school was formed?