‘I’m not sure I believe you.’

Fry looked at Cooper more closely. ‘Are you all right, Ben? Look, don’t worry too much about John Lowther’s death. You did your best to help him. It was the system that let him down, not you.’

‘There’ll be an enquiry. It might decide that I did the wrong thing. There’s only my word for what happened.’

‘You have a witness,’ said Fry. ‘Georgi was there.’

‘No, he didn’t see what happened,’ said Cooper. ‘I told him to stay back on the stairs.’

Fry looked at Kotsev, who gazed back at her impassively.

‘On the contrary,’ he said. ‘I saw everything.’

‘You can’t have done,’ said Cooper. ‘Georgi, there’s no need –’

‘I will tell the story, if I’m called upon. Ben acted well. He was a hero.’

Cooper flushed, uncomfortable with both the sentiment and what seemed to be Kotsev’s misguided loyalty.

‘Let’s get on with it, shall we?’ he said.

He couldn’t help being sceptical about what Fry hoped to achieve in Matlock Bath tonight. A suspect loose among the crowds, strolling through Derwent Gardens with all these families? It didn’t bear thinking about. The risk to the public represented an operational nightmare.

DI Hitchens had made the right decision, in Cooper’s view. No responsible senior officer would authorize an attempt to carry out an arrest in these circumstances. The most they could do safely was to keep Mullen under surveillance – and even then it would be at a distance. So no heroics. Follow him until he was in a location where the situation could be safely contained. Oh, yes. And pray he didn’t get away again.

‘Oh, and make sure you all stay in touch,’ said Fry. ‘That’s what the radios are for.’

‘Yes, how come you manage to get these radios and ear pieces issued, if we’re here unofficially?’ asked Murfin.

‘Gavin, haven’t you learned when not to ask questions?’

They started from the northern end of the village and separated, taking the riverside walk and the parade of shops in pairs. The village really was getting packed. This was the last night of the illuminations, and the night would climax with a fireworks display from the top of High Tor.

Tomorrow, the Heights of Abraham would close for the winter. The cable cars would stop running, the gift shops would shut, and the terraces of the Hi Café and Summit Bar would be left empty. The clocks went back an hour in the morning, and winter would have arrived.