The farmer put a trail camera on the field shelter to catch a fox, and what it caught was a rota. A horse cannot sleep properly standing up. He can doze on his feet for hours, with the leg locked, and he does, but the deep sleep, the kind with dreams in it, only comes lying flat, and a horse will not lie flat unless something he trusts is on its feet nearby. It is why a lone horse goes short of sleep and gets strange, and why a herd takes it in turns, one down and one up, all night, without anybody arranging it. Hector slept on his feet for two years in that field before he lay down at all. The donkey was in the shelter every night of those two years, standing in the dry corner he chose on the first afternoon, and the farmer had assumed that was the whole arrangement. The camera fires on movement. 11 nights of it, stamped to the minute. 00.40. Hector lies down. Flat out, on his side, in the mouth of the shelter with his legs stretched into the yard. Nelson is in his corner, upright, ears out. 01.25. Hector gets up. Shakes. Walks 6 feet to the doorway and stands in it, square, facing the lane. 01.31. Nelson goes down. Chest to the straw, legs folded, chin resting on the ground, which is as far down as a donkey mostly goes, and his eyes shut, and his ears, which have not been still in four years, finally stop. 02.50. Nelson up. Hector, who has not moved from the doorway, walks back in and lies down flat. And so on. Night after night. A seventeen-hand horse who stood guard over nothing for seventeen years and was never once relieved, standing the watch over a sleeping donkey, and being stood down by that donkey an hour later, every hour until light. The fox came on night 6. It walked across the frame at 03.12 and Nelson, who was on, turned his head, and the fox left the frame considerably faster than it had entered it. Hector slept through that. He was off duty. The farmer has eleven nights on a memory card and has watched all of them. He has not put the camera back out, on the grounds that he now knows what happens in that shelter after dark, and it is nobody's business but theirs. Nobody told either of them to do it. A horse takes his turn because a horse always has, in every herd there has ever been. A donkey does not keep watch for anybody. He keeps it for one.