Among the lords of Thames House and Vauxhall Cross, the riverfront headquarters of MI5 and MI6, Grigori Bulganov had always been a source of much fascination and considerable debate. Opinion was diverse, but then it usually was when the two services were forced to take positions on the same issue. He was a gift from the gods, sang his backers. He was a mixed bag at best, muttered his detractors. One wit from the top floor of Thames House famously described him as the defector Downing Street needed like a leaky roof-as if London, now home to more than a quarter million Russian citizens, had a spare room for another malcontent bent on making trouble for the Kremlin. The MI5 man had gone on the record with his prophecy that one day they would all regret the decision to grant Grigori Bulganov asylum and a British passport. But even he was surprised by the speed with which that day came.

A former colonel in the counterintelligence division of the Russian Federal Security Service, better known as the FSB, Grigori Bulganov had washed ashore late the previous summer, the unexpected by-product of a multinational intelligence operation against one Ivan Kharkov, Russian oligarch and international arms dealer. Only a handful of British officials were told the true extent of Grigori’s involvement in the case. Fewer still knew that, if not for his actions, an entire team of Israeli operatives might have been killed on Russian soil. Like the KGB defectors who came before him, Grigori vanished for a time into a world of safe houses and isolated country estates. A joint Anglo-American team hammered at him day and night, first on the structure of Ivan’s arms-trafficking network, for which Grigori had shamefully worked as a paid agent, then on the tradecraft of his former service. The British interrogators found him charming; the Americans less so. They insisted on fluttering him, which in Agencyspeak meant subjecting him to a lie-detector test. He passed with flying colors.