Black ops / Stephen Leather.

Spider Shepherd's MI5 Controller, Charlie Button, has gone rogue, using government resources to get revenge on the men who killed her husband. Spider is told to betray her. Worse, he's asked to cooperate with his nemesis at MI6, Jeremy Willoughby Brown, in taking Charlie down. And he will have to cross the assassin, Lex Harper, currently on the trail of two Irish terrorists, who may be able to lead him to his ex-boss. Meanwhile, Spider's sixteen-year-old son is caught with drugs, expelled from school and threatened with prosecution. But the drug police offer Spider a deal: go undercover, unmask a local dealer and his son will go free. Spider has no option but to cooperate. But is he any better than Charlie, using work resources to resolve personal issues? There's little time to debate because another high profile mission is about to engulf him. President Vladimir Putin is about to visit the UK and a father who lost his son on the downed Malaysian plane over the Ukraine holds Putin directly responsible for his death and wants revenge. Along with everything else, it's down to Spider to stop the assassination of a head of state on British soil.