By Guto Thomas BBC Wales Diplomatic Correspondent

Click here for more information on the cases Introduction Paul Robeson Nicholas of Glais Marco Berni Detainment camp in Rhyl

Robeson was an open critic of the policies of the US Government and openly supported some communist ideals.

Having toured extensively in the 1930s and 40s, he became a high-profile performer behind the Iron Curtain.

The files released by the National Archives in Kew relate to an invitation to perform for miners in south Wales.

Robeson's role as a member of the National Association for the Advancement of Coloured People caused deep embarrassment for the US Government.

But it seems that Robeson's activities did not necessarily strike British Intelligence as being particularly threatening.

In 1943, for example, a report from the secret Intelligence Service (SIS or MI6) noted that "Robeson is known to be rather gullible ... he is rather strongly anti-white and slightly anti-British ... he is a crank on the colour question".

Such remarks are a clear indication of the prevailing attitudes within the British Establishment of the time.

Nevertheless, as a direct consequence of his activism, Robeson was told in August 1950 to give up his passport.

A spokesman for the US state Department was quoted in the London Evening Standard, that allowing Robeson to continue to travel "would not be in the interest of the United States".

Robeson enjoyed great support at this time from the Communist Party of Great Britain, and these MI5 files provide further evidence that the phones were being tapped and letters were being intercepted and copied.

Among the papers is a record of a phone conversation on 15 September, 1951, when "Margaret Jarvis" telephoned the Communist Party Headquarters in Temple Bar, to ask for details about an invitation that had been sent to Paul Robeson.

The MI5 file notes that "she was told that he had been invited to be the guest of the miners at the Miners' Eisteddfod which was being held at Porthcawl in Wales on October 3rd. He was applying for a passport."

Paul Robeson's application was refused. Six years later, he did participate at the 1957 Miners Eisteddfod - but not in person.

Likely refusal

He sang at that now famous event, from his own apartment in New York, via a trans-Atlantic telephone hook-up.

And it is therefore supremely ironic that the attempts of the Eisenhower Government to silence Robeson, actually achieved the opposite of their objective, and secured his place in history.

But the MI5 files also reveals that even had Robeson been allowed to leave the United States in the early 1950s, then it's highly unlikely that he would have been granted access to the United Kingdom.

MI5 believed there was a powerful case for refusal, because of the "security angle".

JH Marriott noted in the Security Service file in July 1951 that "the project of getting him over here under the pretext of a demand for his musical and cultural services is one in which the Communist Party have been interesting themselves".

He also argued that if these efforts were successful, then "there is no doubt that the Party would be gratified".