According to some of his friends, George Orwell was paranoid. In the mid-30s he thought Catholics were spying on him; during the Spanish Civil War he thought communists were shadowing him. In Nineteen Eighty-Four, Winston Smith, relentlessly scrutinised by Big Brother, embodies that sense of persecution.

But Orwell's paranoia, it seems, was justified. The Soviet secret police were watching him in Barcelona in 1937, and now, thanks to documents just released, we know he was also under surveillance by Special Branch and MI5 as early as 1929, while living "down and out" in Paris. Interestingly enough, unlike his many rightwing critics, British spies concluded that he was not a Communist, despite having "advanced" and "unorthodox" opinions.

The detail in these reports is fascinating - a passport photograph of him sporting a strange-looking Hitler moustache while serving as an Imperial policeman in Burma in 1927; an offer of work by the forerunner of the Daily Worker while in Paris. Another document notes that he had tattoo marks on the backs of his hands - not evident from published photographs.

Adrian Fierz, son of the friend who helped Orwell find his first publisher, spotted the tattoos and asked about them. "They were," he recalled, "blue spots the shape of small grapefruits - one on each knuckle."

As this information was on Orwell's 1927 passport it can be presumed he acquired the tattoos in Burma. He was never a properly "correct" member of the Imperial class - hobnobbing with Buddhist priests, Rangoon prostitutes and British drop-outs. As Orwell himself noted, rebellious Burmese tribesmen thought tattoos gave magic protection from British bullets, and, as he himself grew more rebellious, perhaps he felt in need of his own protection against official hostility. The tattoos were probably a sign to members of the British establishment in Burma that he was not "one of them" - an attitude he sustained throughout his writing career. That attitude, highly fruitful for his writing, was also what made him a suspect to the intelligence authorities.

· Gordon Bowker is the author of George Orwell, published by Abacus.