The Crime Trade (Tina Boyd #1) by Simon Kernick

When Operation Surgical Strike goes horribly wrong, suspicion quickly falls on one of the officers involved: Stegs Jenner. No ordinary undercover cop, Stegs is a man who's always lived life on the edge.

Now he decides to go it alone.

DI John Gallan and his partner DS Tina Boyd are part of the subsequent investigation.

What they cannot know is that their enquiries will take both of them into the heart of one of London's most notorious criminal gangs - and one of them into the rifle sights of the enemy.