Reactions to the knowledge that Orwell had acted as an informant for the British Empire have been mixed, with some people crediting Orwell's actions to mental illness, others labelling Orwell's List as a "snitch list", and some writers theorising that Orwell's suspicion of numerous African, homosexual, and Jewish people within his list signified bigotry. Academic Norman MacKenzie, who knew Orwell personally and considered him a friend, lived long enough to discover that Orwell had reported him to the British secret service on suspicion of being a secret communist. MacKenzie responded to learning that Orwell had reported him, and credited Orwell's actions to his degrading mental state caused by Tuberculosis. Alexander Cockburn was far less sympathetic, labelling Orwell a "snitch" and a bigot for the information included in Orwell's notebook, another list of suspected communists that came into the possession of the IRD. This notebook created by Orwell which contained 135 names, was also found to have been held by the Foreign Office. Within this document, Orwell describes African-American Civil Rights leader Paul Robeson as a "very anti-white...U.S Negro".