Frederic Pryor, who has died aged 86, was an expert on comparative economies and the author of 13 books who, as a 28-year-old graduate student became caught up in a famous 1962 Cold War prisoner exchange that was dramatised in Steven Spielberg’s Bridge of Spies (2015).

The film, which Pryor criticised as full of inaccuracies, was based on the true story of the American lawyer James Donovan (played by Tom Hanks), who was enlisted to negotiate the release of Gary Powers (Austin Stowell) – a US pilot whose spy plane had been shot down over Soviet airspace in May 1960 – in exchange for William Fisher, aka Rudolf Abel (Mark Rylance), a British-born KGB spy held by the US.

Donovan insisted on a two-for-one deal, also demanding the release of Pryor (Will Rogers), who had been arrested and held for six months without charge in East Germany.

Pryor had arrived in Berlin in 1959, pursuing a doctorate from Yale University on the foreign trade system of the Communist bloc. In the film he is shown being arrested by Stasi officers after trying to help a blonde woman to cross the newly built Berlin Wall. In fact, he recalled, he had been in Denmark at the time of its construction in mid-August 1961 and “didn’t know any beautiful blondes in Berlin”.