[10][11] He is alleged to have spied for at least four different great powers,[1] and documentary evidence indicates that he was involved in espionage activities in 1890s London among Russian émigré circles, in Manchuria on the eve of the Russo-Japanese War (1904–05), and in an abortive 1918 coup d'état against Vladimir Lenin's Bolshevik government in Moscow.

According to a Soviet secret police dossier compiled in 1925,[20] he was perhaps born Zigmund Markovich Rozenblum on 24 March 1874 in Odessa,[a][20] a Black Sea port of Emperor Alexander II's Russian Empire.

[32] Evidence indicates that Rosenblum arrived in London from France in December 1895, prompted by his unscrupulous acquisition of a large sum of money and a hasty departure from Saint-Maur-des-Fossés, a residential suburb of Paris.

[32] The French newspaper L'Union Républicaine de Saône-et-Loire reported the incident on 27 December 1895: A dramatic event occurred on a train between Paris and Fontainebleau.... On opening the door of one of the coaches, the railway staff discovered an unfortunate passenger lying unconscious in the middle of a pool of blood.

[39] He created the Ozone Preparations Company, which peddled patent medicines,[39] and he became a paid informant for the émigré intelligence network of William Melville, superintendent of Scotland Yard's Special Branch.

[18][52] The Russian-controlled Port Arthur lay under the ever-darkening spectre of a Japanese invasion, and Reilly and his business partner Moisei Akimovich Ginsburg turned the precarious situation to their benefit.

[53] Reilly achieved even greater success in January 1904 when he and his Chinese engineer acquaintance, Ho Liang Shung, allegedly stole the Port Arthur harbour defence plans for the Japanese Navy.

[62] In Ace of Spies, biographer Robin Bruce Lockhart recounts Reilly's alleged involvement in obtaining a newly developed German magneto at the first Frankfurt International Air Show (Internationale Luftschiffahrt-Ausstellung) in 1909.

Having prepared his cover identity by learning to weld at a Sheffield engineering firm,[66] Reilly obtained a low-level position as a welder at the Krupp Gun Works plant in Essen.

[73] Later biographers believe that Reilly, while lucratively engaged in the munitions business in New York City, was covertly employed in British intelligence in which role he may well have participated in several acts of so-called "German sabotage" deliberately calculated to provoke the United States to enter the war against the Central Powers.

[9] Thus Reilly arrived on Russian soil via Murmansk prior to 5 April 1918 where[81] he contacted the former Okhrana agent Alexander Grammatikov, who believed the Soviet government "was in the hands of the criminal classes and of lunatics released from the asylums".

[88][89] In 1918, behind-the-scenes helpers such as ... Sidney Reilly, the erstwhile Russian double agent who was operating on Britain's behalf, were involved in the formulation and execution of various attempts to snatch both Russia and the [Romanov family] from the Bolsheviks.

[95][91] At the time, the dissembling American Consul-General DeWitt Clinton Poole publicly insisted the Cheka orchestrated the conspiracy from beginning to end and that Reilly was a Bolshevik agent provocateur.

[100] A former Socialist Revolutionary Party member, Savinkov had formed the UDMF consisting of several thousand Russian fighters, and he was receptive to Allied overtures to depose the Soviet government.

[101] In contrast to his previous espionage operations, which had been independent of other agents, Reilly worked closely while in Petrograd with Cromie in joint efforts to recruit Berzin's Latvians and to equip anti-Bolshevik armed forces.

[9] Reilly arranged a meeting between Lockhart and the Latvians at the British mission in Moscow while purportedly expending "over a million rubles" to bribe the Red Army troops guarding the Kremlin.

[94] At this stage, Cromie,[103] Boyce,[74] Reilly,[104] Lockhart, and other Allied agents allegedly planned a full-scale coup against the Bolshevik government and drew up a list of Soviet military leaders ready to assume responsibilities on its demise.

[105] Unperturbed by these raids, Reilly conducted meetings on 17 August 1918 between Latvian regimental leaders and liaised with Captain George Alexander Hill, a multilingual British agent operating in Russia on behalf of the Military Intelligence Directorate.

[95] On 28 August, Reilly informed Hill that he was immediately leaving Moscow for Petrograd, where he would discuss final details related to the coup with Commander Francis Cromie at the British consulate.

[103] The Cheka detachment then arrested over forty persons who had sought refuge within the British consulate, as well as seizing weapon caches and compromising documents which they claimed implicated the consular staff in the forthcoming coup attempt.

[126] Hill later wrote that Reilly, despite narrowly escaping his pursuers in both Moscow and Petrograd, "was absolutely cool, calm and collected, not in the least downhearted and only concerned in gathering together the broken threads and starting afresh".

Reilly identified four principal factors in the affairs of South Russia at this time: the Volunteer Army, the territorial or provincial governments in the Kuban, Don, and Crimea, the Petlyura movement in Ukraine, and the economic situation.

"[135] Reilly's reference to events in Odessa concerned the successful landing there on 18 December 1918 of troops from the French 156th Division commanded by General Borius, who managed to wrest control of the city from the Petlyurists with the assistance of a small contingent of Volunteers.

Reilly found White officials, who had been given the job of helping the Russian economy get better, "helpless" in coming to terms with "the colossal disaster which has overtaken Russia's finances, ... and unable to frame anything, approaching even an outline, of a financial policy".

[136] On 18 May 1923, after a whirlwind romance, Bobadilla married Reilly at a civil Registry Office on Henrietta Street, in Covent Garden, Central London, with Captain Hill acting as a witness.

Nevertheless, Cook concedes that Reilly previously had been a renowned operative for Scotland Yard's Special Branch and the Secret Service Bureau which were the early forerunners of the British intelligence community.

[149][150] (In the 1973 book The Gulag Archipelago, Russian novelist and historian Alexandr Solzhenitsyn states that Richard Ohola, a Finnish Red Guard, was "a participant in the capture of British agent Sidney Reilly".

"[137] Two months later, on 17 January 1926, The New York Times reprinted this obituary notice and, citing unnamed sources in the intelligence community, the paper asserted that Reilly had been somehow involved in the still ongoing scandal of the Zinoviev letter,[6] a fraudulent document published by the British Daily Mail newspaper a year prior during the general election in 1924.

[citation needed] In a review of the programme, Michael Billington of The New York Times noted that "pinning Reilly down in 12 hours of television is difficult precisely because he was such an enigma: an alleged radical, yet one who helped to bring down Britain's first Labour government in 1924 by means of a forged letter, supposedly from the Bolshevik leader Grigory Zinoviev, instructing the British Communists to form cells in the armed forces; a Lothario and two-time bigamist who was yet never betrayed by any of the women he was involved with; an avid collector of Napoleona who wanted to be the power behind the throne rather than to rule himself.

After their affair had concluded, Voynich published in 1897 The Gadfly, a critically acclaimed historical novel set in Italy under Austrian rule in the 1840s, whose central character is allegedly based on Reilly's early life.