All his fears of the last few weeks rushed back to his mind, freezing him still. All his fears of the last few weeks rushed back to his mind, freezing him still.

The third lock had been locked, even though Oleg never had the key to it. The third lock had been locked, even though Oleg never had the key to it.

I am combining these two sentences since I believe it's a little more natural.

Though Oleg had never had the key to it.

Alone, this is not a complete sentence.

By the time the two KGB men had wired up the whole flat, ithere remained only one thing left to do: sprinkle radioactive dust on the clothes in the closet. By the time the two KGB men had wired up the whole flat, there remained only one thing left to do: sprinkle radioactive dust on the clothes in the closet.

By the time the two KGB men had wired up the whole flat, ithere remained only one thing to do: sprinkle radioactive dust on the clothes in the closet. By the time the two KGB men had wired up the whole flat, there remained only one thing to do: sprinkle radioactive dust on the clothes in the closet.

A few hours later a senior rRussian intelligence officer landed at the Moscow airport from London. A few hours later a senior Russian intelligence officer landed at the Moscow airport from London.

A few hours later, a senior rRussian intelligence officer landed at the Moscow airport, arriving from London. A few hours later, a senior Russian intelligence officer landed at the Moscow airport, arriving from London.

He had been summoned back to be officially appointed as thea London rezsident—the head of the KGB intelligence station in London, overseeing everyall of the illegal soviet operations in the UK. He had been summoned back to be officially appointed as a London resident—the head of the KGB intelligence station in London, overseeing all of the illegal soviet operations in the UK.

He had been summoned back to be officially appointed as the London rezsident—the head of KGB intelligence station in London, overseeing every illegal sSoviet operation in the UK. He had been summoned back to be officially appointed as the London resident—the head of KGB intelligence station in London, overseeing every illegal Soviet operation in the UK.

Colonel Oleg Gordievsky was at the height of his career; he had risen through the soviet ranks and was still tippinterested toin takeing up higher positions. Colonel Oleg Gordievsky was at the height of his career; he had risen through the soviet ranks and was still interested in taking up higher positions.

I hope I understood this correctly! That he was interested in higher positions, I mean.

Colonel Oleg Gordievsky was at the height of his career; he had risen through the sSoviet ranks and was still tipped to take upvying for higher positions. Colonel Oleg Gordievsky was at the height of his career; he had risen through the Soviet ranks and was still vying for higher positions.

Despite that, as Gordievsky walked through the airport, he felt a terror mounting inside him; he was actually a British spy. Despite that, as Gordievsky walked through the airport, he felt a terror mounting inside him; he was actually a British spy.

Codenamed “NOCTON”, he'd proved to be one of the most valuable spies in history. Codenamed “NOCTON”, he'd proved to be one of the most valuable spies in history.

Still, his abrupt summoning to Moscow had raised concerns among his British handlers. Still, his abrupt summoning to Moscow had raised concerns among his British handlers.

If he returned as the official KGB London rezsident, then the West would have hit the jackpot, b. But if the KGB had set a trap, Gordievsky would lose his life. If he returned as the official KGB London resident, then the West would have hit the jackpot. But if the KGB had set a trap, Gordievsky would lose his life.

This sounds more natural as two sentences rather than one long one.

If he returned as the official KGB London rezsident, then the West would hit the jackpot, but. However, if the KGB had set a trap, Gordievsky would lose his life. If he returned as the official KGB London resident, then the West would hit the jackpot. However, if the KGB had set a trap, Gordievsky would lose his life.

However, in an extreme act of bravery, Gordievsky uttered thise words, “I will go back".” Once out of the airport, he took a cab to his flat on 220 Leninsky Prospekt. However, in an extreme act of bravery, Gordievsky uttered the words, “I will go back". Once out of the airport, he took a cab to his flat on 220 Leninsky Prospekt.