The rest of the group, as I looked around, camera clicking, reminded me of an extended family at Christmas, or on a picnic maybe. I felt as if I’d stumbled into somebody’s front room or garden. A couple of the gorillas were grooming one another, one was dozing and others were absently stripping leaves to eat. The two young ones off to one side were rough-and-tumbling through the foliage. It appeared a scene of lounging contentment to me. So I was baffled when Innocent said, ‘Something’s strange.’

‘Strange? They’re magnificent!’ insisted Amelia.

‘But Spenser’s not here,’ said Patience.

‘What? Who’s Spenser?’

Innocent explained: ‘The silverback. He’s the head of this family. But I can’t see him, or Annabel and her baby.’

Marcel, who had skirted the group, now came back with a worried look on his face and spoke hurriedly to Innocent in French. I caught one phrase I understood, gravement malade, and though I didn’t know who he was referring to, I got the gist: somebody was badly sick. ‘Agité, très agité!’ he went on.

Xander was about to explain what that meant when the situation became obvious. A female gorilla moved in among the troop carrying an infant. It was obviously sick, limp across her forearm, its head canted back. I wondered if it was in fact dead, until I saw its lolling head roll to one side. One of the baby’s arms flopped forward. It was missing a hand, the stump still raw. Seeing the wound, I winced.

‘Can we help it?’ asked Amelia.

Innocent shook his head.

‘Why not?’ said Caleb.

A crashing sound cut off his answer. The foliage behind the troop shook and exploded. A huge gorilla, almost twice the size of the next biggest, shot headlong into the clearing. His back was a slab of muscle dusted in silver fur. It shimmered as he jockeyed sideways with the momentum of a small car. He thumped the ground in front of him, then rocked back on his haunches and beat his chest, making an astonishing percussive sound like two coconut halves being whacked together. It echoed over the noise of the forest. This was Spenser. I couldn’t believe the size of him. The other gorillas had seemed so solid and powerful, but this silverback dwarfed them. Without realising I’d done it, I’d copied Patience and shrunk low to the ground in the face of his display. Her head was bowed. I looked at my hands in my lap. They were quivering.

Yet Caleb was still standing beside me, arms folded across his chest. ‘It’s just for show,’ he explained to Amelia, suddenly an expert, though his voice sounded a bit thin. ‘Nothing to worry about.’

In a low murmur Innocent said, ‘He’s upset. We must be respectful.’

‘Everyone knows they’re nature’s gentle giants,’ Caleb said.

‘Even so, he’s defensive of little Redmond, with the injury.’