The rhino followed as van Steenis led the way to the open-air enclosure. Directed by van Steenis, the two policemen moved along a sloping walkway that climbed out of the stables and circled high above the edge of Dennis’s compound. Van Steenis continued to chat to the animal as if he was a domestic pet while he chewed through a bed of hay on which the food supplement had been emptied.

‘Isn’t he dangerous?’ Cottesloe called across.

‘No. Dennis is as gentle as a pussycat. White rhinos like him are much more placid than the smaller black rhino species, except when calves are about. Besides, he knows me and his other keepers by our scent.’

‘You know that dead body,’ Wickens muttered to Cottesloe. ‘Wasn’t it wrapped in wire?’

‘That’s what I heard. But I haven’t seen it.’

‘See over there?’ He pointed to a hefty roll of wire mesh fencing stuffed down behind metal railings at the far end of the rhino’s compound. ‘What if the bloke had been caught in that, and the rhino leaned against him?’

Cottesloe turned to him, a sceptical smile on his broad face. ‘You fancy yourself as a detective, don’t you?’

Wickens shrugged. ‘There’s a lot of ways of being squashed in a zoo, that’s all.’

‘Sure, but mostly accidental. If that happened I can’t see they would just dump the victim in the Thames.’

They left the walkway as van Steenis made his way back into the stable block. He led them out towards the herpetology building. They passed a rough concrete pool, wired off from the track.

‘I’m going to build a roof on this in the next couple of years, so we can make a tropical crocodile pond.’

‘Where do you get the crocs from?’ Wickens asked.

‘We got some young Nile crocodiles rescued from a French zoo that went into bankruptcy. They need special certificates to be moved, but it was a lot easier within the EU because there is common certification. They are microchipped, like dogs, believe it or not. When they’ve grown a bit I shall put them in here.’

‘It’ll be carnage,’ Wickens said, with boyish enthusiasm.

‘No. It’s much easier to have a gang of Nile crocs than salties, because the Nile boys have a clear pecking order and don’t fight among themselves. That really helps at feeding time.’ He stared over the railing reflectively. ‘Boy, I learned my lesson with Australian saltwater crocs. I had two females, Betty and Nora, but Nora bullied the other, bit her tail, and then chewed off a foreleg. Eventually she killed her. Nora now has to have an enclosure on her own, over the back.’ He gestured with his arm. ‘She is nearly ten feet long now, must weigh half a ton, and I wouldn’t trust her an inch.’