We agreed it was no good calling yourself a Christian, promising to return good for evil and love your enemies, if you took part in a vast horror of lies, hatred, and slaughter.

I appeared before a tribunal while I was still at school. This had an unpleasant side. I was turned out of the study which I shared with other prefects, and the boys would hit me on one cheek and ask whether I would offer the other. This mild persecution rather flattered my vanity.

I wrote a defence in the school magazine, which was refused because it was thought to reflect badly on the school's reputation. It was passed round, and some of the older boys read it and treated me with a kind of deference. One simple-minded athlete looked at me with genuine contempt.

Since then I have often asked myself whether he was right, whether the men who became C.Os. were really those who were, consciously or subconsciously, more afraid of a bayonet in their guts than other people. Analysis might show that C.Os. had more than the usual repulsion from pain and death. But the matter was more complicated than that. The demand for courage came in France, not in England, where the herd, and particularly one's womanfolk, usually made it difficult to refuse a uniform.

For my part, my predominant fear was that I might miss the war. No doubt I was glad that I was less likely to be killed than other people, but though I was in many ways a coward I have no memory of being frightened of death. Physical courage scarcely enters the question when one is eighteen.

In my ward, there were twenty-five men who were literally half dead. They were very much alive in their top halves, but dead below the waist. The connection between their brain and their natural functions were broken. They could feel nothing in their hips or legs, and in spite of being constantly rubbed with methylated spirit, they had bedsores you could put your hands in.

I tracked down my ambulance train at Sootteville railway siding, not far from Rouen. It was an ancient train, with modern coaches only in the centre, and coaches and fourgons without corridors at both ends.

Two of us worked in the ward, a couple of doctors and two or three nurses lived in the central coaches. Each coach was arranged to take twenty lying patients, with floor-space on which to dump five more on stretchers if necessary. Alternatively, forty or fifty men would sit in the coach if they were walking cases.

There were two pails for soup or cocoa or tea, a brass urn for drinking water. A primus stove was the most important object; a good deal of life turned on the question of whether one could get enough paraffin by fair means or foul. Another major objective was to get as many decent blankets as possible. If you could steal a soft khaki blanket of the type used for officers you were proud of yourself. At each hospital base you swiftly and surreptitiously swapped new blankets for the bloodstained and muddy ones that came into the ward.

The front was comparatively quiet when I first joined the train. The Battle of the Somme was over, and we travelled up that stricken valley without incident. Everywhere shell-holes, barbed wire and stumps of trees. Places like Ypres, and many villages whose names we saw on the railwayside, had disappeared. Arras had a line of latticed ruins, and a church which looked as if it was still a place for visitors - until one got closer and found it was a shell.

We would load at a casualty clearing station behind the lines, and travel down very slowly indeed to Rouen or Etaples. Perhaps it would be four in the morning when we loaded. We would reach our base at seven at night, unload, sweep out, clear up, and would be preparing for some sleep about ten, when a message would come that we were evacuating a load of Blighty convalescents from Boulogne at five a.m. Then we got out our disgusting groundsheets again, lowered the beds for the sitting cases and dozed until the load arrived of cheerful patients bound for England, with arms in slings, legs in bandages, or head-wounds that weren't too serious. We would take them to Boulogne, unload them, scrub out the ward, shake out the blankets, ready for another slow progress to the back of the front.

Harold Smith said he would exclude from the franchise every C.O. who had not taken up arms for his country in this time of emergency. Philip Snowden asked the Hon. Member why he was not serving, as he was of military age? Harold Smith said that was a matter for his conscience (loud and ironical cheers).

I recall the wounded as being incredibly patient and unhappy. The one thing they asked, hopefully, prayerfully, was whether they'd caught a 'Blighty' this time. Was their wound bad enough to get them home? Did I think it might get them out of the war altogether? That was perhaps too much to hope for. After all, they were damned lucky to be wounded. Most of their company or battalion would never come home.

A common dodge was to shoot your foot through a sandbag so that the powder did not show. A guard was put to watch anyone who damaged himself. What I recall most from that time is the total loss of belief that the war had any object; it was just an incredible calamity that had to be endured. They were men without faith or hope. They were bitterly critical about people at home. They never grudged your comparatively cushy job. They would give you a dig in the ribs, "Oh, you're a Quaker, are you? Good luck to you. I wish I'd thought of that dodge myself." You'd been smarter than they had. A disconcerting view as long as you remained any kind of idealist.

It was our first experience of mustard gas. The men we took were covered in blisters. The size of your palm most of them. In any tender, warm place, under the arms, between the legs, and over the face and neck. All their eyes were streaming, and hurting in a way that sin never hurts.

Suddenly, as we were arranging our game of football, someone noticed that an engine was arriving for our train. We bundled in, and up to the casualty clearing station. Something new. The Germans had broken through. No one who did not know the stability of trench war can realise the astonishment of the German push. Thousands and hundreds of thousands of men had died pushing the line forward a hundred yards; that had been the rule for the past two years. And here was a push of thirty miles and an army crumpled up in a day or two. French soldiers shouted at us, "What's happened to the bloody Fifth Army?" The British had lost the war. It was said not to be safe to go out because the French were so angry.

Up at the line again we became aware in the early morning mist - I remember it vividly today - of thousands of bodies, acres and acres of them, lying out on the ground, with scraps of German grey or British khaki hanging out over the stretchers. They were very few bearers, and so we loaded the train ourselves, making no distinction between England and Germans; every inch of the train was full.

We are now on the run again. No longer can I talk of sunshine, novels, magazines, games - men have been fighting, killing each other. I do not ask God to stop this hideous, awful warfare: I ask men to. I do not know whether it is cowardice that makes me shrink from fighting: if so I am proud of being a coward. I do not think I'm afraid of being killed - I am terribly afraid of killing. Whether I should be a common coward on the battlefield of course I do not know. No-one can who has not faced it.

Amiens is a strange and awful sight. On the ground, hundreds of stretcher cases lying, and hundreds of "walking wounded" sitting about. They have been constantly loading trains for eleven days now. We get a load of 25 stretchers, some of them serious, and six sitters. We leave about 6.0 and reach Rouen at 4.30 next morning! Completely fagged out with watching cases all night, sleep all morning of 30th.

The British army, like the French, might have followed the Russians and mutinied in 1917-18. The arrival of the American army - brash, unpopular as it was - meant a change in mood. The Allied counter-offensive seemed astonishingly well organised and tidy.

Delays in demobilisation and lack of jobs brought disillusion. Before long the men were singing 'Homes for Heroes' and cursing Lloyd George. The Canadians and the Australians fought in their camps. The only time in my life when revolution in Britain seemed likely was in 1919.