'On George Orwell in Spain.'
Gerald Frost at The New Criterion.
"Orwell’s Eton drawl had probably not impressed Harry Pollitt, the general secretary of the British Communist Party, who suspected, perfectly correctly, that Orwell was likely to prove 'politically unreliable' and that if he were to write about the war, he could not be relied upon to follow the party line. Pollitt therefore declined to provide the documentation that would have gotten Orwell across the Franco-Spanish border and into the International Brigades, abruptly ending their interview."
See Orwell, Animal Farm, in Great Books of the Western World (second edition, 60 Vol., 1990) volume 60.