From my logbook;
Washington
17/4/72 LHR-IAD G-ASGG
19/4/72 IAD-LHR G-ASGG (18/4/72 local time)
24/5/72 LHR-IAD G-ASGH
26/5/72 IAD-LHR G-ASGH (25/5/72 local time)
02/6/72 LHR-IAD G-ASGR
04/6/72 IAD-LHR G-ASGR (03/6/72 local time)
Entebbe
05/5/71 EBB-LHR G-ARVK
14/5/71 EBB-LHR G-ARVL
The 'Standard' made it non-stop using the short runway (the new, long one had not yet been built).