He was a policeman. He worked at the airport. And he was the source of the most accurate intelligence we had. It was on the strength of his warnings that we were able to interdict the powerful 82 mm mortars before they could be deployed. And it was intelligence he supplied that allowed us to prevent bigger attacks. Attacks using vehicle-borne IEDs, against anything from the fortified gates of a FOB to a school. These boys were indiscriminate.

He had a brother in al Shabaab. It wasn't unusual. To many Somalis the solution to the problem of feeding a family was terrorism. His had been the police.

Thing was, they lived in the same run-down area of western Mogadishu. It was a place where secrets were hard to keep. A place from which mortar attacks and suicide bombs and erratic rifle fire came thick and fast. And where both sides downed tools five times a day to pray together. The modicum of give and take was just enough to permit survival. But cooperation had its limits.

People emulate. Somehow they absorb the standards and values by which they are surrounded. Years of fighting the government with bombs and bullets, of justifying the killing of women and children with arcane passages from the Qur’an had made of one brother an evil man. The other, from long exposure to the law had gradually developed a powerful moral compass.

That day he had all the details. It was, I suspected, a conscious decision. I knew he had not taken it lightly. He knew what was planned was wrong. And he knew that in telling me he had crossed a line. The risks of discovery were high. And the consequences grave.

He took my hand as he left. Smiled briefly and then was gone.

The previous week I’d met his beautiful young wife. A picnic on the rubbish fringed white sands of Mogadishu beach. She was effervescent and cheeky. Like many Somalis she was determined not to be worn down by the hardships they endured. A struggle justified only by the accident of their birth.

That afternoon the three sons she had given him frolicked among the rocks and surf. I remember the way the evening sun lit their young faces, illuminating their excitement. The simple happiness of a day at the beach. I remember the pride in her eyes. And the faint trace of fear in his.

Later that day I wrote the report. The operation was successful. The intelligence was good. A scruffy white Toyota Hilux, mildly up-armoured by a welder with half a dozen sheets of plate steel was found parked in a side street not far from the seat of Government in Villa Somalia. Close to a tonne of high explosives lay in fertiliser bags under an old tarpaulin thrown carelessly over its load compartment. It was a busy area. Pedestrians and shoppers packed the streets, soldiers kept guard, politicians came and went. It would have killed dozens. Injured a hundred or more.

All forms of contact ceased with my policeman after that day. I have no idea what happened to him. I never saw his wife or their children again.

Our intelligence collect was never quite the same. Neither was I.

In most stories, conflict is scaffolding. The villain impedes the hero. The obstacle slows the plot. Resolution arrives with victory: someone wins, someone loses, the story ends. This is not conflict. It is obstruction with a tidy answer.

Real conflict has no tidy answer. It is the state of being bound, simultaneously, to two things that cannot both be honoured. Operational necessity and the dutiful man with fear in his eyes. Moral duty and the three sons he never mentioned. The day when everything was correctly done and nothing was right.

David Baboulene put it plainly: the reader does not turn the page to see what happens. They turn it to find out how a person lives with what they have done. That is the conflict worth writing. Not obstacle. Obligation against obligation, with a cost on every side.

The book I am finishing is built entirely from moments like that one. So is anyone's life, if they are honest about it.

More on that next time.