Graham fast-forwarded the footage by a few minutes once the audience had found their focus. There was movement in the bottom right-hand corner of the screen, leaves and branches displaced in ill-defined shades of grey, then a patch of darkness appeared where the bush had been. A figure stepped through and out onto the pavement: slim, graceful, unmistakably female, even with only a shaky silhouette on view. The hair was either short or tied back and the line of her neck was clear. She leaned down.

‘We think she’s brushing off debris from the hedge,’ Graham said as the figure straightened again. ‘And here, she does something with both hands then reaches into her coat. It seems likely that she’s removing gloves and putting them in her jacket pockets to avoid looking suspicious. That night wasn’t exactly warm but it wasn’t necessarily gloves weather. She exits down the street and we lose sight of her. After that we were unable to catch her on any other CCTV on nearby roads, so we assume she got into a vehicle at some point, or even called a cab.’

Ava stared at the screen as if the woman might reappear. In spite of the darkness and the horrible pixellation of the footage, there was something about the woman that struck a chord with her. A familiarity, something to do with the way she moved. How she’d cocked her head to one side and smoothed her hair before walking off down the road. She closed her eyes and tried to catch the threads of her subconscious mind that were already slipping away.

‘If she was wearing gloves, how did her DNA get onto the cushion?’ someone asked.

‘We think from her saliva, possibly from the effort of pushing the cushion over his face, or from spittle flying as she spoke to him during the event,’ Graham replied. ‘Full DNA results from all the Bruce Jenson exhibits only came back this morning. It’s possible we might be able to tell a bit more about her, in generic terms, in a few more days.’

He nodded at Ava, ceding the floor.