The Dragon's Tail -- Adam Williams

Harry Airton, a Scottish fisherman, has China in his blood. A chance encounter with a spook during the Korean War gives him the opportunity to return to the land of his birth and serve his government at the same time. They hatch a long-term plan to create the perfect spy: a triple agent with a cover that cant be broken, because its genuine.

What Harry doesn't realise is that if he is setting the perfect trap, the Communist Chinese may also be finding the perfect bait. And that as the Cold War escalates and China marches towards Cultural Revolution and the end of the twentieth-century, the fates of two people who love each other are entirely unimportant.