Some authors just write about it. Chris Ryan has been there, done it, and lived to tell the tale.
Agent 21 is the first in the action-packed adventure series by the real-life SAS hero. When Zak Darke's parents die in an unexplained mass murder he's left alone in the world.
That is until he's sought out by a mysterious man: 'I work for a government agency,' the man tells him. 'You don't need to know which one. Not yet. All you need to know is that we've had our eye on you.
There's a possibility you could help us in certain . . . operational situations.'Zak becomes Agent 21. What happened to the 20 agents before him he'll never know.
What he does know is that his life is about to change for ever . . .