A Skype call with Dr Chen’s sister in Adelaide, Australia promised to clear up some of the contradictions. Mrs Wendy Ho had first requested to speak to British detectives early that morning, but because of its multiple addressees the email had dropped into Gillard’s junk mail folder. Although it was three p.m. in Britain when the detective responded, Mrs Ho got straight back to him. She had clearly been awake even though it was 11:30 p.m. in Adelaide.

The woman who Gillard saw on the screen was a bespectacled middle-aged Chinese lady with a kind face. Behind her was a wall hung with family photographs.

‘Mrs Ho, thank you so much for agreeing to talk to us at such short notice. I hope you don’t mind but I am recording this to help with the case.’

‘No worry,’ she said, with a twang of Australian showing through the Chinese accent. ‘I no sleep so well since I told he dead.’ The woman lifted to the screen a framed photograph of a handsome and confident-looking naval officer in a white uniform and peaked cap, with golden epaulettes. ‘This is my brother Wei-Ling. Is this man you found?’

Gillard could see that the portrait had been taken decades ago. ‘Do you have anything more recent?’ he asked.

She picked up a phone and after swiping a few times showed him a picture of a dapper grey-haired fellow, smiling, standing under a cherry tree heavy with blossom. It was hard to say for certain if it was the same man. Gillard needed a comparison. He carefully slid one of the gory CSI pictures face down back along his desk, only lifting it face up behind his screen to be sure that the Skype camera didn’t pick it up. The two images side by side were not conclusive. A little elasticity with the truth was required.

‘It certainly could be him, Mrs Ho. What have you been told about your brother’s death?’

‘Just that he found in River Thames. Maybe suicide.’

‘Did your brother have suicidal feelings?’ Gillard asked.

‘He depress, since he heard about cancer. No cure. But I no think he kill himself. He very brave man.’

‘I’m sure he was, Mrs Ho.’

‘Mr Gillard, how long Wei-Ling been in UK?’

‘He arrived at Heathrow Airport on June seventeenth, his body was found on the morning of June twenty-second. We don’t know much about what he did between those two dates. Is there anything you can tell us?’

‘He planned to go to nanotech conference in Oxford, I knew that. But I thought he not go, because of cancer.’

‘As far as we know, he didn’t go. In fact, we don’t know what he did do. Did he have any friends in Britain or any contacts here that you are aware of?’

‘I send you list. I email to them already to ask. They say he no tell anybody what he plan.’