Karen Armstrong, perhaps the world’s best-known ex-nun, has ­written elegantly and sometimes ­passionately on many subjects. She is ­associated with a generally revisionist account of the Christian faith, a mixture of retrieval and reinterpretation. Such accounts used ­regularly to cast Paul as the villain who ­muddled up the pure, simple message of Jesus, and Armstrong admits that 30 years ago, planning a television series, she expected to take this line herself. What stopped her then, and motivates her now, is the attempt to locate Paul within his historical context, leading to a much more sympathetic account of “‘this difficult, brilliant and vulnerable man”. Armstrong never fully explains in what sense she thinks Paul has been “misunde