Isaac Tut, 16, has finally settled down at school to sit his first exams. But it has taken him five years to adjust from being abattle-hardened veteran in the Sudanese People’s Liberation Army, writes Peter Moszynski.

When I first met him he was 11 and had already spent two years on the front line, including Operation Jungle Storm, the army’s failed assault on the south Sudanese capital, Juba. Following the rebel defeat he and his group trekked some 400 km to join a rival faction.

When he left the rebels he described the conditions that led him to desert. He said he was so heavily laden he could scarcely walk. “First they give you the pack. Then you must carry water.” He sags at the knees. “Then you are given ammunition.” Another sag. “Then you must take your rifle. It was so hot and so heavy I could hardly move.”

When they escaped from Juba they couldn’t find any food or water, and most of his fellows died along the way. Of 38 who set out, only nine survived the trek.

He was discovered by an aid worker, who took him to Kenya, but she died in a car crash a few weeks later. Isaac found himself alone again, a refugee in a strange country.

I spent some time looking after him, and took him on a few trips to take his mind off things. Once we visited friends who had a large telescope on their veranda, and his eyes immediately lit up. He ran over to it, saying:

“I know what this is. You put the shell in here” - he covered his ears - “You pull the rope, and bam!” He had never seen a telescope before, but he knew perfectly the firing routine for a 122mm mortar.

But both government and rebels in Sudan have now apparently agreed to stop using under-age fighters. The Coalition to Stop the Use of Child Soldiers said: “The SPLA has finally realised that it has created a generation of children who cannot read or write and know only the respect that is earned by the barrel of the gun.”