The best moment is on a chilly Christmas morning at the zoo of the Jardin des Plantes in Paris, as you walk the avenues that Rilke once walked. As you sniff the odours of damp vegetation, you realise that there is life here beyond the hysterical noise of children. This is because plants and animals do not yet recognise the sacred space that is Christmas. They believe Christmas day to be like any day, they go about their business in the customary manner, looking, yawning widely, eating, defecating undemonstratively, and also sleeping.

It is here that we come upon them, small examples of that species we have long wanted to observe. They are penned into artificial environments, fragments of man-made woodland consisting of a tree or two, some lengths of rope, straw, and a certain amount of undulating ground made from toughened, painted polystyrene which simulates wilderness. It is the most constricted of artificial habitats. They are happy. They have not noticed that it is not where their kind have customarily lived and moved. They are as happy here as anywhere else, we think as we crowd together on the far side of the floor-to-ceiling meshing - they must not get out - and stare at them in wonderment. They hang upside down above our heads, clinging to the limb of a tree, these creatures we have so long wanted to see. We thought for a long time that they were extinct - they look as if they should ...