‘He said to me it was just a job… that sometimes involved a few bodies lying about’

an ex-SAS bodyguard, in part for the kudos. My best friend’s dad went to run security at a diamond mine in Sierra Leone (which was apparently “very lively”). Another close acquaintance, who lives in an ivy-clad former rectory, runs diplomatic protection for foreign governments.

For many, this provides a decent income but very few get rich, even moderately so. There is almost universal contempt for the tiny number of former troopers who try to become celebrities and make big money from publicising their (often imaginary) exploits.

BUT, as in any group of human beings, there are exceptions to the rule. I have heard of some ex-SAS men who have turned to drink or drugs (which is rare), but it’s more common for them to seek isolation and a simple life deep in the Herefordshire countryside – or even to turn to religion.

My school friend’s dad became a Sufi – an adherent of the mystical branch of Islam that Cat Stevens embraced. It was his way of reconciling the dual aspect of his character. He was, he discovered, both a warrior and a deeply spiritual person.

This is something we find hard to understand in the present day but, in the Middle Ages, knights were as much men of God as of war.

I recently asked a former SAS man what it was like to be a trained killer. He shrugged and said it was just a job… that sometimes involved a few bodies lying about. He enjoyed his service and was happy to do it; not necessarily, I sensed, through any great feeling of patriotism or duty but because he was born to it. He is one of the warrior caste who have always existed and always will. And in order for the rest of us to sleep soundly in our beds – to paraphrase George Orwell – we need rough men like him.

I’m not sure I’ll ever get used to the fact that the bloke who lives down the lane might be parachuting into Isis-held territory at night, fighting a hand-to-hand battle and escaping by the skin of his teeth.

But truth is always stranger than fiction – if you’re looking for an SAS hero, you’ll most likely find him in a Herefordshire cottage with roses around the door.

●●The Black Art Of Killing by Matthew Hall (Michael Joseph, £14.99) is published tomorrow. For free UK delivery, call Express Bookshop on 01872 562310 or order via expressbookshop.co.uk