The marching season - Daniel Silva

It is the first uncertain years of the Northern Ireland peace process. In Belfast, Dublin and London three simultaneous terrorist attacks shatter the hope that the bloodshed finally may be over. Although suspicion immediately falls on Catholic Republicans, it quickly becomes clear that the perpetrators are Protestant Loyalists, a new terror group called the Ulster Freedom Brigade. They have but one goal - to destroy the peace process.
Michael Osbourne, the hero of Silva's second novel, The Mark of the Assassin, has quit the CIA, bitter and disillusioned. He is living quietly in New York, struggling with the responsibilities of fatherhood and the tedium of early retirement. But when the President chooses his father-in-law, former US Senator, to be the next American ambassador to Britain, Osbourne is drawn into battle with some of the most ruthless and violent men on earth.
Osbourne is rehired by the CIA with the mission of preventing the Ulster Freedom Brigade from destroying the peace proccess. What Osbourne does not know is that the terrorists have hired the world's deadliest assassin; none other than Jean-Paul Delaroche, the title character in The Mark of the Assassin, to murder the ambassador.
The Marching Season takes place in the backstreets of West Belfast, the rolling hills of Armagh and, as the locale for the assassination a country estate in Norfolk.