LS has got it; the other flight was indeed once-weekly on an Iraqi Airways Trident, operating Baghdad-Istanbul-Prague-Berlin SXF-London LHR. Iraqi had been a somewhat unusual purchaser of some of the few Trident 1s that were built for export, they carried on from their earlier Viscounts. Bit of an extraordinary flight though. I wonder how many actually boarded it at Schonefeld to go to London. The scheduled time was much faster than LOT posted on their IL-18 turboprop.
ia70-3.jpg (1106×1267) (timetableimages.com)