I just came across more on that 1977 SR-71 static display at Mildenhall in Paul Crickmore's
Lockheed Blackbird: Beyond the Secret Missions (Revised Edition 2016).
Colonel 'Buz' Carpenter narrates:
As a postscript, about two weeks later we were informed that our TDY at Mildenhall had been extended to support the Air Tattoo celebrating the Queen’s Silver Jubilee. A two-day open house would attract well over 100,000 visitors and the SR-71 would be on its first British public display since setting the speed record from New York to London in 1974. The SR-71 would be part of the static display, but roped off so people could not touch the aircraft.
We had been advised to watch for representatives from the Soviet Union and Eastern satellite countries trying to get too close to the aircraft and securing material samples. To prevent the Russians or anyone else from exploiting the display, no sensors were left on the aircraft, all fuel had been removed from the tanks and the aircraft was heat soaked to ambient temperatures to prevent infrared cameras from discovering the secrets of the aircraft’s internal structure and support systems.
As we four crewmembers were standing around the aircraft answering questions from the crowd, sure enough the Russians showed up in numbers. They took numerous regular and infrared photos and some of the Russians even had hidden microphones. They were a sight to see, coming up like a covey of quail. It looked like the Salvation Army had outfitted them. Their dress sense was that from a 1930s movie about American mobsters. They were attired in bulky double-breasted suits made from rougher cloth than one normally sees, and all clustered around each other waiting for their leader to act. The head of the Soviet delegation, a former MiG-23 fighter pilot, was quite relaxed and talkative in his demeanour and invited John and I to sometime drop in on Vladivostok in the Far East as a gesture of peaceful relationships. We just quipped, ‘Please forward that request to our State Department.’ The British open house audiences are much more aviation literate than their American counterparts. Tough aeronautical questions were often asked as we stood by the aircraft in the static display, but a great time was had by all, with wonderful weather and spectacular flying demonstrations.
Actually, one of my Navy skippers did cross-deck with the Russians in Vladivostok in about 1978.