It appears from the MI 5 files for the post-war era in Britain, that as several members of the International Brigade Association (IBA) had long suspected, IB vets were systematically spied on by Britain's internal political police service M15. MI 5's website reveals that this occurred in the Cold War years following the end of World War II , see
Philby-Below (Bandaged) in Spain, his transport had come under attack from Republican Forces Below (ii) as a Senior MI 5 Officer-
Philby-below (iii)- as he appeared in a Commemorative Stamp in the USSR .
"File ref KV 5/46-58
The thirteen reconstructed files of Security Service information about the British International Brigade Association (IBA) now released give a wealth of detail about the organisation and its activities from 1941 to 1954.
The files show that nearly all Security Service records on the IBA prior to June 1941 were destroyed at an early date, and there is therefore no contemporary information about the IBA from the Spanish Civil War period. Instead, the files focus on the propaganda and campaigning work of the IBA on behalf of Brigade veterans and against the Franco regime. Through intercepted correspondence of leading figures such as Nan Green (to April 1947 when the warrant was suspended) and phone calls, and through reports of meetings around the country, a detailed history of the development of the IBA can be reconstructed. The records of liaison with the Secret Intelligence Service show that in the post-war years most of the correspondence passed through Kim Philby's hands. There is a brief Security Service summary of the IBA's history at serial 570a in KV 5/58.This scrutiny of IBA activity, may well have involved liaising with Spanish intelligence, as well as phone tapping, and perhaps most disturbingly 'reports' of meetings throughout the country. Whether or not the meetings reported on were internal IBA meetings or not is not made clear, although some diligent historian of IB affairs, and I know a few, will no doubt be able to reveal this now that the files are open to examination. Disturbing stuff, men and women whose 'crime' was that they took up arms against fascism in the years 1936-1939, were scrutinised secretly by the British state well after the Second World War, even more disturbing is the possibility that information concerning ongoing anti-fascist resistance in Franco's Spain may have been gleaned from this operation.It also appears that all the reports on this operation ended up on the desk of one Kim Philby , who no doubt, it can be reasonably assumed given his loyalties, would know exactly what should be done with the most sensitive and potentially damaging information .In fact it is ironically the case that Philby himself, could, had the truth been known at the time, have qualified as a veteran of the anti-fascist struggle in Spain, having been posted there in his earliest days as an operative deep inside Franco occupied Spain, to provide intelligence to the Comintern on the feasibility of an assasination of the Fascist leader.