You can't trust AI I'm afraid; foreign participation at Farnborough in 1968 was limited to several aircraft with British major components such as engines (including the unfortunate RR Tyne-powered Breguet Atlantique which stalled and crashed at the end of its demonstration...). No Mil Mi-6, no Soviet participation at all - Farnborough became properly international in 1970 or 72 and the Russians attended for the first time in 1988.
The Mi-26 was at Farnborough '92.