<<LHR (LED..) to my knowledge do not operate in parallel at all.>>
Heathrow can, and does, operate parallel approaches but only under certain conditions when both runways are in use for landing. This usually occurs in the early morning when there are lots of arrivals and few departures. Rules are that radar separation must exist between landing aircraft, but not vortex separation on final approach between aircraft on different runways. In good visibility and daylight radar separation between aircraft on separate runways can be dispensed with if the pilots can see each other and can provide their own separation.
All the above with the usual proviso that things may have changed since I retired!!