Thanks chevron.
Barcelona ACC/APP had a ASR-5 radar equipment. The report did not mention any secondary radar. After reading the report, I understand that rules laid down by ICAO for radar identification at that time, did not include an SSR equipment as a mandatory equipment. In the “Recomendations” chapter of the report, they say “the spanish autorithies have already made a suitable provision in this respect, so that identification can be properly checked by more than one method”.
You say you were on duty when the accident happened. Did West Drayton have a secondary surveillance radar at that time? What I mean is if an SSR was a common equipment by those times in other countries. It is well known that Spain, generally speaking, was backward Europe in terms of technology in those times, but I don't know the real situation regarding to air traffic control.