Sir – Klaus Fuchs may not have been the only ‘big fish’ netted by Sonya, the Kidlington spy (Feature, August 12). In his book, Too Secret Too Long, the veteran espionage writer, Chapman Pincher, suggests that Sonya moved to the Oxford area specifically to make contact with a long-time Soviet mole then working at MI5’s emergency wartime HQ at Blenheim Palace.

The alleged mole was Roger Hollis, who went on to become head of MI5 from 1956 to 1965. During Sonya’s time in Summertown, Hollis was living about a mile away, in Garford Road, which Pincher finds ‘rather difficult to accept as sheer coincidence’.

But if Sonya was ‘running’ Hollis, they would have been unlikely to have met in person. Pincher’s intriguing theory, based on information from a Soviet defector, is that they may have left messages for each other in a gap between two gravestones in St Sepulchre’s Cemetery in Jericho. The cemetery is close to where they lived and would certainly have been ideal for secret letter drops.

The suspicion that Hollis may have been a Soviet spy first emerged in the 1960s and has divided the intelligence community ever since. Some agree with Pincher, while others dismiss the allegation as fantasy.

Indeed, there is a theory that the Russians may have deliberately incriminated Hollis in order to throw MI5 off the scent of the real traitor. But in the world of mirrors things are rarely as they seem. Sonia, in her memoirs, denied that she ‘ever had anything to do’ with him. But, then, she would, wouldn’t she?

Christopher Farman, Deddington