Konstantin Volkov (died 1945) was an NKVD agent and would-be defector.
In August 1944, Konstantin Volkov, Vice Consul for the Soviet Union in Istanbul, sent a letter to Chantry Hamilton Page, the vice consul in the British embassy, requesting an urgent appointment. Page decided the letter was a "prank" and ignored it. A few days later, on 4th September, Volkov, accompanied by his wife Zoya, arrived in person and asked for a meeting with Page.
Page did not speak Russian and so he brought in John Leigh Reed, first secretary at the embassy, to translate what Volkov had to say. Reed later reported: "I was serving in our embassy in Turkey in 1945.... One morning this Russian walks into reception looking very nervous and asks to see the acting consul-general, Chantry Page. The Russian is Konstantin Volkov, Page's opposite number in the Soviet embassy. I'd done my Russian exams so I get the job as interpreter. Anyway, it turns out that Volkov is really an NKVD officer and he has decided to defect. He says he wants a laissez-passer for himself and his wife to Cyprus and £27,500. In return he is offering the real names of three Soviet agents working in Britain. He says two of them are working in the Foreign Office, one the head of a counter-espionage organization in London."
He asked for $27,000 and a promise of political asylum, stating that if his demands were met he was willing to expose 314 Soviet agents in Turkey and 250 Soviet agents in Britain. More importantly, he said there were two British diplomats in the Foreign Office and another man (Kim Philby) in a very high ranking position in the Counter Intelligence Section of the British Secret Intelligence Service who were spying for the Soviet Union. He demanded an answer within three weeks, and insisted that Istanbul not send his information by cable because the Soviets were reading British Cipher System traffic. The news was sent to Sir Stewart Menzies, head of the SIS (commonly known to the media and the public as MI-6) by a diplomatic courier. In London, the matter was given to the head of the Russian Section, Kim Philby, who took the necessary steps and flew out to Istanbul.
Meanwhile, Volkov returned to the Soviet Consulate, from whence he quickly disappeared. He was last seen as a heavily bandaged figure being hustled aboard a Soviet transport plane bound for Moscow. Kim Philby, who was one of the Soviet moles whom Volkov's defection would have exposed, arrived 21 days late. The Consulate officials who had met with Volkov were enraged by Philby's delayed arrival, believing his actions criminally incompetent. Years later, after his own defection to the Soviet Union, Philby admitted to having informed his NKVD contact about Volkov prior to his own departure for Istanbul. He contemptuously described Volkov as, "a nasty piece of work," and referred to the incident as the greatest obstacle he ever faced.