Behind Sheep Rock was a high viewing tower from which it was possible to see the front of the Chicken House, indeed the whole of the Zoo, and I thought it looked like ten pfennigs well-spent for anyone wanting to make sure that he wasn’t about to walk into a trap. With this thought in mind I was meandering away from the Chicken House, and towards the lake when a youth of about eighteen, with dark hair and a grey sports jacket, appeared from the far side of the Chicken House. Without even looking around he quickly picked the Gerson bag out of the wastepaper basket and dropped it into another carrier, this one from the Ka-De-We store. Then he walked briskly past me and, after a decent interval, I followed.

Outside the Moorish-style Antelope House the youth paused briefly beside the group of bronze centaurs that stood there, and, giving the appearance of one engrossed in his guidebook, I walked straight on to the Chinese Temple, where, hidden by several people, I stopped to watch him out of the corner of my eye. He came on again, and I guessed that he was making for the Aquarium and the south exit.

Fish were the last thing that you expected to see in the great green building that connects the Zoo with Budapester Strasse. A life-sized stone Iguanadon towered predatorily beside the door, above which was the head of yet another dinosaur. Elsewhere, the walls of the Aquarium were covered with murals and stone reliefs that depicted the kind of prehistoric beasts which would have swallowed a shark whole. It was to the Aquarium’s other inhabitants, the reptiles, that these antediluvian decorations were in fact preferable.

Seeing my man disappear through the front door, and realizing that the Aquarium’s dark interior would make it easy to lose him, I quickened my pace. Once inside I saw how much more probable than possible this actually was, since the sheer number of visitors made it difficult to see where he had gone.

Assuming the worst, I hurried towards the other door that led out on to the street, and almost collided with the youth as he turned away from a tank that contained a creature that looked more like a floating mine than a fish. For a few seconds he hesitated at the foot of the great marble stairs that led up to the reptiles before walking down to the exit, and out of the Aquarium and the Zoo.