Uncommon Enemy by Alan Judd

From a prison cell, in which he has been held on suspicion of breaking the Official Secrets Act, Charles Thoroughgood awaits not only his bail, but also the reappearance of the woman whom all the major roads in his life have led back to. After his years in the army and then with MI6, Charles has begun a new chapter in his life with the Secret Intelligence Agency, shadowing the movements of a suspected double agent. Charles knows that he has nothing to hide, and as he casts his mind over the course of recent events, he begins to suspect a more sinister motivation, both personally and politically, behind his incarceration…