MI5 monitored socialist writer George Orwell for more than two decades, but did not believe he was a mainstream communist, records have revealed.
Orwell did not agree fully with the Communist Party, MI5 said
A Scotland Yard Special Branch report in January 1942 said the author of 1984 had "advanced communist views".
However, an MI5 officer responded that Orwell "does not hold with the Communist Party nor they with him".
A file from the National Archives also shows MI5 did not object to him having a wartime job at a military base.
Orwell was vetted for the post as a correspondent for the Sunday Observer at Allied Forces Headquarters in North Africa.
The Special Branch report said: "This man has advanced communist views and several of his Indian friends say that they have often seen him at communist meetings.
"He dresses in a bohemian fashion both at his office and in his leisure hours."
The MI5 officer rang the inspector in charge of the sergeant who wrote the report, to question what it meant.
From the call it emerged that Orwell - referred to in the documents by his real name Eric Blair - was thought to be an "unorthodox communist" who did not agree fully with Communist Party views.
The officer from the security service wrote: "I gathered that the good sergeant was rather at a loss as to how he could describe this rather individual line hence the expression 'advanced communist views'.
"It is evident from his recent writings - The Lion and the Unicorn - and his contribution to Gollancz's symposium The Betrayal Of The Left that he does not hold with the Communist Party nor they with him."
'Bit of an anarchist'
Orwell is best known for books including 1984 and Animal Farm, which criticise totalitarianism, and other works attacking inequality, including Down and Out in Paris and London and The Road to Wigan Pier.
The records show Orwell first came to the attention of intelligence service MI6 in 1929 when he was in France and offered to become Paris correspondent for the Workers Life.
In 1942, a record described him as "a bit of an anarchist in his day and in touch with extremist elements".
He had "undoubtedly strong left-wing views, but he is a long way from orthodox communism", it added.
Other MI5 records released by the National Archives reveal a rather basic approach to intelligence gathering.
Kent policeman Pc Ivan Smith resorted to hiding in a toilet to listen in on apprentices from the Royal Navy dockyards at Chatham discussing strike action in December 1941.
American musician Alan Lomax was put under surveillance by MI5 as a potential communist, and his BBC TV shows in the early 1950s were monitored by Special Branch.
The BBC was informed that Lomax was in contact with the Hungarian press attache in London, although that could have been linked to his interest in folk dancing.
The records reveal that a German spy - Argentine Ernesto Hoppe - was involved in plans to transport Nazi valuables to South America.
However, he was arrested in Gibraltar in October 1943 after a tip-off and interrogated at Latchmere House, south London.
After going on the run from a military hospital and trying to contact the Argentine ambassador, he was recaptured and admitted his role in the plot.
In other records, it is revealed that a 1945 edition of The Naturist magazine was examined by MI5 for "hidden writing", which would have been shown up by a solution of soda and water.
Norwegian spy Hans Larsen was interrogated by the British, also at Latchmere House, in May 1945.
A copy of the magazine he had in his possession was tested for the writing among the pages of naked women and articles titled Naturism in the United States and All the Year Round Natural Fitness.