Frank Day was the Engineering Manager of the trial and Nic Nicolas was the trial ATCO. I missed out on this trial - probably elsewhere in the country since radars were being upgraded on a grand scale.
Contacted my colleague Janice, a usual fountain of all knowledge re 'old' radar flight trials, and even she has failed other than:-“I cannot remember any report or what happened, all under wraps as I remember, but during that time there were calls of sightings of UFO's around LAP which, I think, were in the press!!”
RaRadar - CAAFU Hs748 for the actual trial of the H23. Seem to recall we upset the residents of Bedfont when ATC put the aircraft in a low level holding pattern while you undertook approach to the old cross runway.... it was in the middle of the night!!