Excerpt from A Spy Among Friends by Ben Macintyre, plus links to reviews, author biography & more

In the end, Philby's entry into the secret services turned out to be as straightforward as that of Elliott, and by much the same informal route: he simply "dropped a few hints here and there" among influential acquaintances and waited for an invitation to join the club. The first sign that his signals had been picked up came on the train back to London after the retreat from France, when he found himself in a first-class compartment with a journalist named Hester Harriet Marsden-Smedley, of the Sunday Express. Marsden-Smedley was thirty-eight years old, a veteran of foreign wars, and as tough as teak. She had come under enemy fire on the Luxembourg border and witnessed the German surge across the Siegfried Line. She knew people in the secret services and was said to do a little spying on the side. She found Philby charming. She did not beat about the bush.

"A person like you has to be a fool to join the army," she said. "You're capable of doing a lot more to defeat Hitler."

Philby knew exactly what she was alluding to and stammered that he "didn't have any contacts in that world."

"We'll figure something out," said Hester Marsden-Smedley.

Back in London, Philby was summoned to the office of the foreign editor of the Times, to be told that a Captain Leslie Sheridan of the "War Department" had called, asking if Philby was available for "war work" of an unspecified nature. Sheridan, the former night editor of the Daily Mirror, ran a section of MI6 known as D/Q, responsible for black propaganda and disseminating rumors.

Two days later, Philby sat down to tea at St Ermin's Hotel off St James's Park, just a few hundred yards from MI6 headquarters at 54 Broadway, with another formidable woman: Sarah Algeria Marjorie Maxse, chief of staff for MI6's Section D, which specialized in covert paramilitary operations. The D stood for "destruction." Miss Marjorie Maxse was chief organization officer for the Conservative Party, a role that apparently equipped her to identify people who would be good at spreading propaganda and blowing things up. Philby found her "intensely likeable." She clearly liked him too, for two days later they met again, this time with Guy Burgess, an old friend and Cambridge contemporary of Philby's who was already in MI6. "I began to show off, name-dropping shamelessly," wrote Philby. "It turned out I was wasting my time, since a decision had already been taken." MI5 had conducted a routine background check and found "nothing recorded against" him: young Philby was clean. Valentine Vivian, the deputy head of MI6, who had known Philby's father when they were both colonial officials in India, was prepared to vouch personally for the new recruit, giving what may be the quintessential definition of Britain's old boys' network: "I was asked about him, and said I knew his people."

Philby resigned from the Times and duly reported to a building near MI6 headquarters, where he was installed in an office with a blank sheaf of paper, a pencil, and a telephone. He did nothing for two weeks except read the newspaper and enjoy long, liquid lunches with Burgess. Philby was beginning to wonder if he had really joined MI6 or some strange, inactive offshoot, when he was assigned to Brickendonbury Hall, a secret school for spies deep in Hertfordshire where an oddball collection of émigré Czechs, Belgians, Norwegians, Dutchmen, and Spaniards were being trained for covert operations. This unit would eventually be absorbed into the Special Operations Executive (SOE), the organization created, in Winston Churchill's words, to "set Europe ablaze" by operating behind enemy lines. In its early days, the only thing the agents seemed likely to ignite was Brickendonbury Hall and the surrounding countryside. The resident explosives expert mounted a demonstration for visiting Czech intelligence officers but set fire to a wood and nearly immolated the entire delegation. Philby was soon transferred to SOE itself, and then to another training school at Beaulieu in Hampshire, specializing in demolition, wireless communication, and subversion. Philby gave lectures on propaganda, for which, having been a journalist, he was considered suitably trained. He was champing at the bit, eager to join the real wartime intelligence battle. "I escaped to London whenever I could," he wrote. It was during one of these getaways that he encountered Nicholas Elliott.

Excerpted from A Spy Among Friends by Ben Macintyre. Copyright © 2014 by Ben Macintyre. Excerpted by permission of Crown. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.