Manhunt — James Barrington

First in a series about a British navy veteran who goes to work for the secret service to bring down a defector threatening Britain's national security.
 
Nobody is ever above suspicion in the ‘wilderness of mirrors' that is the world of intelligence, but when a senior officer goes bad it still hurts. When that senior officer can't be identified, it hurts even more. Conventional detective work to unmask him is going to be too slow, and probably unreliable, so an alternative strategy has to be formulated. With the security of Britain's most secret computer system at stake, and trust a commodity in short supply, a deception operation is set in train to flush out the traitor. Paul Richter, an unemployed ex-Naval aviator, is the unwitting and ultimately expendable bait in the trap. But as the net closes around the traitor in France, a female Russian intelligence officer flees Moscow and the evidence she brings points the finger of suspicion in a very different direction. With time running out, and nobody he can trust, Richter finds himself battling against both the British security establishment and trained teams of Russian assassins with orders to kill both him and the woman he's trying to protect.