The MI5 verdict: Ian McGibbon outlines what Paddy Costello's recently opened MI5 file indicates about why British counter-espionage concluded that he was a Soviet agent.

• Jurisdiction: New Zealand
• Date: 01 November 2017
• Author: McGibbon, Ian

Whatever the truth about Paddy Costellos allegiance, one fact is known: towards the end of his life, MI5 concluded that he was a Soviet agent. There had been suspicions for nearly three decades, of course, but after taking his professorship in Manchester Costello fell off MI5's radar, at least for a time. The focus returned to him in the early 1960s, though not for the commonly supposed reason of his alleged involvement in the Kroger affair--the issue of New Zealand passports to Peter and Helen Kroger (who were in fact Soviet spies Maurice and Leontina Cohen) by the New Zealand Legation in Paris in 1954 when Costello was on the staff; in possession of perfectly forged documents, the Krogers needed no illicit assistance in obtaining the passports. Nothing on Costello's recently released MI 5 file indicates any suspicion falling on him when this was revealed in 1961.

That Costello came under renewed MI5 scrutiny was directly attributable to his wife Bella (Bil). Long known to have been a communist earlier in her life, she was identified as having ordered several children's death certificates in 1960. Acquisition of such...