‘It’s certainly possible to target specific areas. We do it to biopsy tumours that are deep within the brain. We use navigation computers to guide a needle either to obtain a sample or to deliberately cauterize an area with electricity that heats the needle and destroys the tissue at the tip. But we always screw a frame to the skull to keep it completely still and it leaves four small scars on the head, two on the forehead.’ He placed his index fingers on his own head just above his temples. ‘Here and here.’

Bloom felt a jolt of adrenaline. ‘Exactly where Harry has bruised and damaged skin.’

Karene was biting her lip as she studied the images.

‘Don’t you think that’s a coincidence?’ asked Bloom.

The surgeon frowned then moved back to his computer. ‘You’d have to drill a hole in the skull for the needle to pass through. It’s usually the size of a five-pence piece but it could be smaller, maybe five millimetres in diameter? It could be masked by his head injury.’ He pressed a few buttons and the scans changed. He walked over to examine them.

‘But the hole would be visible on the MRI?’ said Bloom.

‘These are the CT scans sent from Exeter Hospital. It would be easier to spot it on these.’ He returned to his computer, flicked through numerous pictures and selected four to display. ‘This is the area of the head trauma. We have cracks to the skull here and here, nothing too drastic but …’ He beckoned for Bloom and Karene to join him. ‘Look at this,’ he said, pointing to a gap in the thick white line. ‘That could be a hole. It’s thicker than the other fractures and completely dissects the skull bone. Do you see?’

‘So, he did have surgery?’ said Bloom.

‘Possibly,’ said Avery.

‘Why has no one spotted this before?’ said Karene.

Avery folded his arms and concentrated on the screen. ‘If this is a hole, it was cleverly masked by his injuries. It’s not unusual for victims of an explosion to have cracks and holes in their skull. You wouldn’t find it unless you were looking for it.’ He went back to the computer and selected the MRI scans again. ‘If he did have surgery to affect his memory, I would expect bilateral lesions on his hippocampus.’ His voice was urgent, excited almost.

‘Damage done to both the right and left sides?’ asked Bloom.

‘Indeed.’ He enhanced the scan until the section he was looking at filled the middle screen on the wall, then he put his glasses on and walked over to study it. ‘Well, well,’ he said.

‘You can see lesions?’ said Bloom.

‘But why are they there? This is a perfectly healthy brain.’

‘To make him forget.’