In Matlock Bath, houses seemed to climb on top of each other in their haste to escape the valley floor. Above them were the two Victorian pleasure grounds on Masson Hill – the Heights of Jacob, the Heights of Abraham. Their biblical slopes were occupied by modern leisure parks now, the fairy-tale shapes of castles and towers poking up among the trees.

For the past twenty years, there had been no need for anyone to slog up the winding paths to reach the hilltop park at the north end of the village. Strings of white cable cars now rode high over the valley from a base station near the railway line, carrying visitors up to enjoy the play areas, the Treetops gift shop, the Hi Café and the Summit Bar. A grey stone tower was visible on the summit, a flag fluttering in the breeze.

The weather had been warm right through into October, which felt wrong in the Peak District. After another dry summer, the trees had burst into an explosion of yellows and golds. Where the turrets and battlements of Lilliput Land Castle had lurked among dense foliage all summer, now they were emerging slowly from a sea of reds and golds. Some of the other features of Gulliver’s Kingdom were being revealed, too, like the chairlift and the campanile on Fantasy Terrace.

Cooper could see the new indoor facility standing out prominently on the hillside. It was designed to stay open during the winter, and it housed everything from Wild West shoot-outs to an ice palace. Or so his nieces told him. He supposed he’d have to take them there one day, when he got some time off.

Turning left out of the aquarium, he called at the neighbouring properties, which happened to be the two villas housing B&Bs. There was a chance that Rose Shepherd had come into Matlock Bath to meet someone who was staying here, although there didn’t seem to be any reason why she should have killed time next door in that case.

Drawing a blank, he walked a bit further up North Parade, where he found another amusement centre and a shop selling hand-made chocolates, both of which were closed.

Across the road was the Jubilee Bridge – wooden planks and iron girders, with an old gas lamp on a central arch. It led across the river to a bandstand and the remains of a switchback. There were more wooded slopes lying above Lovers’ Walk. Their steepness called for erosion controls: log revetments, brush and board hurdles, a dead hedge. Here and there, sycamores and beeches had been felled, no doubt condemned because they weren’t native to Derbyshire.