Past Abergavenny and Crickhowell, the full spread of the Beacons lay ahead. ‘Somewhere among that lot was Kareem’s interrogation centre,’ said Patrick. ‘Let’s hope Marion’s mother’s bearings stand the test of time.’

They rounded the town of Brecon and headed towards a fold of long-backed hills. After a few miles, they came to a narrow lane.

‘I think that’s the turning,’ said Patrick. ‘But let’s climb first. See the whole vista from on high. Survey the battleground.’ She felt him camouflaging his fear.

They wound their way up between long slabs of mountainsides, scarred by ancient gullies where surging rivers once flowed. On the roadside, a leafless, stunted hawthorn tree leant to the east, the casualty of decades of buffeting from the west wind. The only spectators were sheep, the bare green of the hills dotted with a coppice or two on far ridges and the occasional deserted shepherd’s hut. They reached the shoulder over which the next valley stretched, parked and walked up a few hundred yards to the nearest summit. Below them lay a steep fall into a valley which seemed to spread for ever into far vistas of England and Wales.

‘The innocent hills of Britain,’ said Patrick. He breathed deeply, puffing out his chest, and closed his eyes. ‘Let’s go.’

‘Let me check in with the hospital first.’

He frowned. ‘Do you have to?’

She narrowed her eyes. ‘What’s the problem?’

‘Maybe I’m being paranoid – or overestimating their paranoia. But say they’re monitoring the hospital exchange, they get the number of your burner phone.’ He hesitated, then grinned. ‘To hell with it, I am being paranoid. ’Course you should.’

A few minutes later, two miles down the lane they’d located, they came to a gate leading into a driveway and stopped. It led downhill to a square farmhouse of dark stone and mullioned windows.

‘Too small,’ said Sara.

‘And too visible,’ added Patrick.

‘It should be more sunken. We need the solid gates to identify it. The buildings here all seem the same dark grey stone. Elizabeth Green said the end wall of the barn by the entrance gates was whitewashed. But lots of walls have had that done to them.’

‘It could have peeled off.’

They returned to the car and crept along the lane. The description on the map had brought them as far as they could, now it was for their eyes only.