When some of the people blacklisted during the McCarthy era left the United States to find work in the United Kingdom, they might have thought they had left their troubles behind them. But they were wrong. The FBI passed its files on to MI5, the British Security Service, which seems to have accepted the bureau’s judgments without question.

The theater and movie director Joseph Losey was a case in point. Openly a man of the left, he was fingered in Hollywood after the war as a possible Soviet agent. “I was offered a film called I Married a Communist, which I turned down categorically,” Losey reported. “I later learned that it was a touchstone for establishing who was a ‘red’: you offered I Married a Communist to anybody you thought was a Communist, and if they turned it down, they were.” (The film was eventually made as The Woman on Pier 13 by the British-born director Robert Stevenson, who went on to direct Mary Poppins.) Eventually named as a member of the Communist Party, Losey found it almost impossible to obtain employment in the US and settled in Britain in 1953.

MI5 was on his case in a flash. He was, the Security Service asserted, associating with communists in Britain, too. “Losey mixes with the usual Bohemian set of the film and theatre world, which includes many left-wing supporters,” MI5 told the Ministry of Labour, which supervised “aliens” (non-British citizens) looking for work. Losey, the report added, was “very short of money.” But he had done nothing to provide a pretext for deportation, and he was protected by his 1956 marriage to an Englishwoman. When Losey visited the US Embassy in London, he confessed to his past membership in the Communist Party, which he said he had given up. Losey went on to work with the British playwright Harold Pinter on a string of movies that became instant classics, including The Servant, The Go-Between, and Accident.

The actor Sam Wanamaker was another American who came under the surveillance of MI5, which noted that he had been involved with individuals mentioned by the House Un-American Activities Committee. His conversations, it was reported, had “a distinct Communist bias,” and he was an associate of the actor James Robertson Justice “with his Communist views” (Justice had fought for the Republicans in the Spanish Civil War and later appeared in The Guns of Navarone). But Wanamaker stayed in the UK despite MI5’s suspicions and later successfully campaigned for the re-creation of the Globe Theatre in London near its original location, which produced Shakespeare’s plays in an authentic Elizabethan setting, earning him an honorary degree from the University of London and an honorary CBE from the queen.

The Security Service also kept a file on Paul Robeson, the Black singer and actor who played Othello to Peggy Ashcroft’s Desdemona at the Savoy Theatre in 1930. Robeson lived in Britain for much of the 1930s and attracted MI5’s attention by championing a variety of left-wing causes. “He is rather strongly anti-white,” a report from 1943 complained, “and slightly anti-British as the result of a social insult sustained at the Savoy Hotel in London. He is a crank on the colour question.” Robeson returned to the United States in 1939 and inevitably fell afoul of the State Department, which denied him a passport after the war and continued to do so until 1958, preventing him from leaving the country.

MI5’s files, released for public scrutiny piecemeal over the past few years—though in many cases with the names of the informers redacted—provide many other examples of people placed under surveillance because of their (real or alleged) communist views and associations. The veteran historian, novelist, and playwright David Caute has gone through them in detail and produced a book, Red List: MI5 and British Intellectuals in the Twentieth Century, that summarizes their contents person by person. Although it reads a little like a catalog or a biographical dictionary, with too much trivial detail and too little analysis, the book provides a wealth of information about left-wing British intellectuals and artists in the postwar era. Some are more or less unknown, but a good number are quite famous, including the Oscar-nominated actor Michael Redgrave (“very active on the left”) and the composer Benjamin Britten (“a pacifist for many years”).

The Security Service was particularly interested in left-wing historians like Christopher Hill (“He has the appearance of a communist,” a disappointed agent at Harwich reported after Hill disembarked from a ferry, “but his baggage, which was searched by HM Customs, did not contain any subversive literature.”) Hill’s letters were intercepted so clumsily that he noticed on one occasion that an enclosure mentioned in one letter had been delivered to him in an envelope containing a different one. He would later become Master of Balliol College, Oxford, after leaving the Communist Party along with several other Marxist historians—with the notable exception of Eric Hobsbawm, whose seventh and last file in the MI5 collection still hasn’t been released.

Hobsbawm, whose six other files I read when researching my biography, Eric Hobsbawm: A Life in History, was also under suspicion. MI5 stepped up its surveillance and for a time even opened his mail, turning up nothing more compromising, however, than love letters from his married French girlfriend in Paris. The Security Service was especially suspicious of Hobsbawm because he seemed rather foreign (his mother was Austrian, and he maintained contacts with historians on the Continent, including in East Germany). An agent listening in on one of his lectures was unable to find anything more incriminating than the fact that it was “really interesting.” MI5 became excited when it learned that Hobsbawm had visited Spain, at the time still under the dictatorship of Francisco Franco, only to discover that he had been there as a reporter for the New Statesman.

MI5 also kept files on E.P. Thompson, the author of the 1963 classic The Making of the English Working Class, who was found to be “in contact with known communists.” On one occasion it confused him with E.A. Thompson, the historian of late antiquity, describing E.P., somewhat implausibly, as the author of a scholarly work on Attila and the Huns. On opening his letters, the agents must have been somewhat disconcerted to discover that many were essay-length disquisitions, Thompson being as usual totally unable to restrain his verbal exuberance. Particularly dubious in the eyes of the Security Service were his relations with anti-colonial campaigners like Cheddi Jagan, later the prime minister of British Guyana. “Some aliens have stayed with THOMPSON from time to time,” an agent reported in 1958, but the service was unable to identify these suspicious foreigners any further.

The Security Service also took an interest in poets and writers, including Cecil Day-Lewis (nowadays better known as the father of Daniel Day-Lewis), described as being of “not altogether smart appearance in dress.” (MI5 officers took a dim view of any subject who, as they noted of Hobsbawm, “dresses in a slovenly way.”) Day-Lewis became Britain’s poet laureate, a royal appointment, not long before his death in 1972. MI5 opened a file on another poet, Stephen Spender, who was refused a visa to go to Harvard in 1949, though the decision was reversed after protests in the press. Spender had briefly been a member of the Communist Party in the 1930s, which he’d joined after being repelled by the Nazi regime during a visit to Germany. However, he was soon put off by the party’s treatment of the arts as no more than instruments of political indoctrination, and he was dismayed by a leading communist, Harry Pollitt, who, Spender complained, “whenever I met him would say: ‘Why don’t you write songs for the workers, as Byron, Shelley and Wordsworth did?’”

Part of the trouble, for Spender and many of his peers, was that the Communist Party of Great Britain never really accepted the intellectuals into its ranks: The party remained dominated by “donkey-jacketism,” or veneration for manual laborers, whose characteristic clothing was a donkey jacket (a dark blue overcoat with black leather shoulder pads). Yet even if the party often rejected its intellectuals, MI5 treated them as in need of constant surveillance. Spender was monitored even after contributing to The God That Failed, a 1949 collection of essays by ex-communists, including André Gide, Ignazio Silone, and Arthur Koestler. MI5 agents recorded everything, including the entirely inconsequential: A report on Spender dated September 27, 1951, for example, noted that the agents had seen “an odd creature” leaving his basement apartment in London between 1 and 2 am, dressed in white overalls. “They cannot say whether the odd creature is a man or a woman.”

Spender belonged to a group of poets and novelists whose members included Christopher Isherwood, the author of the short novels Mr Norris Changes Trains and Goodbye to Berlin; the novels’ atmospheric depiction of Berlin decadence on the eve of the Nazi seizure of power later formed the basis for the successful musical Cabaret. Isherwood wasn’t a communist, but he was “a member of the Anti-War Movement in the 1930s,” as one agent noted. During Isherwood’s interviews in 1951 with the FBI in California, where he lived, he handed the agents a list of contacts that included Spender as well as the novelist E.M. Forster and the poet W.H. Auden—a document that was duly forwarded to MI5.

Isherwood also pointed MI5 to Anthony Blunt, an art historian who later became surveyor of the queen’s pictures, in charge of the great collection kept at Buckingham Palace and other royal residences. Blunt really was a Soviet spy, unmasked many years later, but on this occasion he got away with it, partly by naming names himself. One of them was David Footman, a former agent with MI6, or the Secret Intelligence Service, who, when I was a grad student at St. Antony’s College, Oxford, served as the college librarian. Footman had the reputation of being a recruiter for the British secret services, and I spent three years waiting for an approach—but, alas, none ever came.

What all these men had in common was that they knew Guy Burgess, who worked at the Foreign Office. Like many of them, Burgess was homosexual, and they knew one another through the clandestine gay subculture within the London establishment. When Burgess was finally revealed, together with Donald Maclean, as a Soviet agent, MI5 suffered “a panic attack of extended surveillance and involuntary interviews,” as Caute puts it. It even placed a phone tap on the apolitical author and literary editor Cyril Connolly, “a member of a circle which included Soviet agents Burgess and Maclean,” predictably without result.

What all of these cases reveal, as well as those of many lesser-known British intellectuals, is above all the futility and stupidity of the secret services, along with their social snobbery and racial prejudices. A case in point was George Orwell, who in the mid-1930s was said to be “conducting Communist activities” because he was meeting with “undesirables” and was published by Victor Gollancz, “a firm which specializes in Left Wing literature.” In fact, the “undesirables” in question were unemployed people in the industrial north of England, whom Orwell was interviewing for his 1937 book The Road to Wigan Pier. MI5 described Orwell’s anti-colonialist opinions, which derived from his early experiences in the colonial Indian police service, as “advanced communist views.” Here was another intellectual who aroused suspicion because “he dresses in a bohemian fashion both at his office and in his leisure hours.”

Yet an officer who took the trouble to read Orwell’s books condescendingly dismissed these reports as written by someone who was a “good Sergeant…rather at a loss.” “Orwell does not hold with the Communist Party nor they with him,” the officer wrote. This better-read agent was not wrong: Animal Farm and Nineteen Eighty-Four were devastating critiques of Stalinist totalitarianism, and Orwell would happily volunteer his services to those monitoring communists and their suspected sympathizers. Not long before his death, he submitted to a secret department of the Foreign Office dedicated to anti-communist propaganda a list of people he thought unsuited to work for it because they were too sympathetic to Stalinism. These more than 35 “cryptos” included not only Spender (“sentimental sympathizer…. Tendency towards homosexuality”), Robeson (“very anti-white”), and Cecil Day-Lewis, but also the historians E.H. Carr, Isaac Deutscher, the novelist J.B. Priestley, the Nobel Prize–winning scientist Patrick Blackett, the actor and film director Orson Welles, the journalist (and future leader of the Labour Party) Michael Foot, and scores more.

While MI5 was spending huge amounts of time and resources pursuing these essentially harmless intellectuals, it ignored the real traitors in the British establishment, men like the Cambridge Five (Burgess, Maclean, Blunt, Kim Philby, and John Cairncross) and the betrayer of Britain’s nuclear arms secrets, Klaus Fuchs, whose activities were revealed by a partnership between the US Army’s Signal Intelligence Service and GCHQ, the agency charged with radio traffic surveillance, not MI5. Like so many MI5 officers, the Cambridge Five had been educated at prestigious private schools, spoke with cut-glass accents, and (with the exception of Burgess) behaved like proper English gentlemen. They didn’t in the end do a huge amount of damage, except perhaps to Britain’s secret services themselves. Caute dismisses them as “material for the ongoing explosion of spy books popular among adults with the hearts of boys.”

Many years ago, the historian Hugh Trevor-Roper, who served in MI5 during the war, penned a biting critique of the Security Service. He described the agents as of “very limited intelligence…by and large pretty stupid, some of them very stupid.” MI5 was full of “metropolitan young gentlemen whose education had been expensive rather than profound and who were recruited at the bars of White’s and Boodles”—two conservative gentlemen’s clubs in London. They wore pin-striped suits and club ties and were suspicious of ideas, insofar as they had heard of them at all. In an odd way, their anti-intellectualism was a mirror image of the anti-intellectualism of the Communist Party. The many other officers who had begun their careers in the Colonial Service were even more blinkered. The use of racist language was common; one senior agent reported in 1950 his belief, after a visit to West Africa, “that the West African natives are wholly unfitted for self-rule.” The Security Service was obsessed with communist “subversion” while, at least until the outbreak of World War II, viewing fascist and Nazi sympathizers like Sir Oswald Mosley (a hereditary baronet) with an indulgent eye.

As for the intellectuals, MI5’s suspicions on the whole did little to damage their careers, except perhaps for limiting their ability to broadcast on the BBC, an institution over which, this book shows, MI5 had a surprising degree of influence. More harm perhaps was done to the careers of the 1,420 junior civil servants identified as “subversive” by the Thatcher government in 1985 on the basis of information supplied by MI5. Most of them were alleged Trotskyists or communists, though there were also a few Scottish nationalists and “black or Asian racial extremists.” They were denied promotions and carefully monitored in their work. Politically, MI5 was firmly on the side of the Conservative Party; Labour politicians were suspect to its agents, especially if they were on the party’s left. The Security Service even kept a file on Harold Wilson, the prime minister from 1964 to ‘70 and 1974 to ‘76, though it has never been released. MI5’s manifest incompetence makes it hard to take these activities very seriously, but the culture wars that it carried on behind the scenes were a feature of British conservatism’s tendency to regard left-wingers as potential “enemies of the people”—one that has persisted to the present day.