Complex sentence: One important liberty taken by the film makers was that, in actual fact, no serving member of the American armed forces was involved in the final escape; the film does concede that it was a mainly British-led operation.
Split into simpler sentences: One important liberty taken by the film makers was that, in actual fact, no serving member of the American armed forces was involved in the final escape. The film does concede that it was a mainly British-led operation.