Callum. In the early days of Gatwick and London Approach the procedural, or Approach, controller would descend aircraft in the holds and often issue instructions to leave the hold. The No 1 Director would then descend the aircraft and once it was clear of other traffic he would hand it to the No 2 Director for pistioning on to the ILS.
PAR was used for talk-down before the days of ILS. When ILS first came into service it was not as accurate as nowadays so PAR was used to monitor all approaches in poor visibility. As ILS became more reliable, PAR was withdrawn from most civil airfields - the Heathrow PAR went in the mid-70s i recall. No PAR equipment existed at West Drayton and does not at Swanwick. At Swanwick and most major ATC units SRAs are carried out using the same radar as used for sequencing. Some airfields do have older, dedicated, SRA radar equipment.
I was at Heathrow in 1975 and I don't understand why yoiu should think that only a procedural controller would ask an aircraft to squawk ident? That is a radar function and only a radar controller would issue that instruction. "Director" is a 100% radar control function.
London Airways - the procedural element - was the "executive" controller who used London Radar so expedite traffic as needed. Later, the control service became wholly radar and all controllers now exercise the radar and procedural aspects.
Shout if you want more info. Some people on here go back a long way.