Thirty years ago, at one of the hinge points of European history, Margaret Thatcher tipped up at the Kremlin for talks with Mikhail Gorbachev. Britain’s prime minister had once described the Soviet president as someone with whom she could “do business”. Now, the foundations of Soviet communism were cracking. Hungary had torn down the barbed wire at its border. East Germans were fleeing westwards. The fall of the Berlin Wall was only weeks away.

For journalists travelling with Thatcher, the visit was memorable for more trivial reasons. After a rapid-fire Japanese tour, the prime minister’s party arrived on a gruelling flight from Tokyo. Thatcher travelled on one of the Royal Air Force’s ageing VC-10s.Decades earlier the aircraft had been at aviation’s cutting edge; by the standards of 1989, it was slow, noisy and, for those squeezed into the back, claustrophobic.

Its limited range meant a refuelling stop at a military air base in bleakest Siberia, where two burly Soviet air force officers joined the party. Were they spies or chaperones? Either way, they would surely report back that the top secret communications equipment carried on the flight resembled nothing so much as a collection of vintage valve radios.