The Cambridge Spy Ring's Sixth Man: Tinker, tailor, soldier ... Irishman?

Newly released MI5 papers have added fresh speculation that second generation Irishman ‘Paddy’ Costello, the son of a Dublin grocer, could have been The Sixth Man in the infamous Cambridge Spy Ring. Writer/researcher Johanna Lowry-O’Reilly looks at the evidence as to whether he was an Irish nightingale or a carrier pigeon?

While MI5 files (KV2/4328-31) released on 11 April 11 greatly extend the intelligence profile of Desmond Patrick Costello, commonly known as ‘Paddy’, they neither fully prove nor disprove the contention that he was the ‘Sixth Man’ at the heart of the Cambridge spy ring in the 1930s.

They do, however, ostensibly negate the 2008 assertions of James McNeish, a fellow native of Auckland in New Zealand. McNeish, an historian, strongly defends Costello against accusations of spying in his book The Sixth Man, which was written without the benefit of these files and has been essentially superseded by them.