Your mention of Diyarbakir made me get the logbooks out. I did an interesting flight from Bahrain to Tehran on 12.09.71 (Argosy XN852) with the SBS in the back. At Tehran we picked up some of the Shah's special forces and set off for Rasht (an airfield on the south side of the Caspian Sea which is actually below sea level). Now getting an Argosy from Tehran to Rasht would have taken all day on an IFR flight plan but my very experienced navigator knew this neck of the woods well from his time on an Embassy Devon based in Amman. He suggested a VFR plan through the Elburz mountains at 6,500 feet (the mountains go up to 18,500 feet). To my amazement, ATC at Meherabad accepted the flight plan without a murmur. After 55 minutes of spectacular scenery we were on the ground at Rasht, offloaded our passengers and so departed for Akrotiri.
We had a day off in Akrotiri and departed on 14.09.71 for Diyarbakir. For the life of me, I cannot remember why we were going there. Perhaps we had spares for a stranded Canberra or something. Anyway, the point of the story is that I can remember being tracked on radar from Diyarbakir for they were worried about us reaching IFR safety height (so were we) for our route back to Bahrain.
My main worry was whether the 40 demijohns of Cyprus plonk which were tied up in two neat rows in the freight bay might have caused a flutter in the dovecot at Diyarbakir but they were all delivered intact to the various messes in Bahrain!