‘I went downstairs to sleep in the flat. It was empty at the time, and Charlotte had made it clear she wished to be alone. Sometime in the night, I heard a noise – it sounded like something falling over upstairs.’ He catches her gaze, watchful and wary, tells her: ‘I didn’t go to investigate.’

‘Why not?’

‘I don’t know. Too drunk, too tired. Weary at the thought of another confrontation. I just turned over and went back to sleep.’

He had slept late. Alcohol made him deeply unconscious.

‘When I woke, half the day was gone. I could hear someone upstairs, banging on the front door and ringing the bell. When I went outside to investigate, some of my neighbours were on the top step, trying to get in. I was confused – bewildered. I had no idea what they were doing there, why they had come. It wasn’t until later that I was told about Mark …’

They’d found her in the kitchen. Blood pooling on the floor. Small footprints tracking blood out into the hallway. A terrible scene.

‘I have so many regrets,’ he tells Leah. ‘That I didn’t react to the noises I heard that night. That I slunk off downstairs, like a coward, and didn’t stay and face up to her accusations. If I had, she would still be alive.’

He pauses to consider this. Then adds: ‘The last words we spoke were in anger. Bitter, hurtful things. We wanted to wound each other, but …’ and the look he gives her now is pressed with meaning and sincerity ‘… I only ever wounded her with words. With my infidelity. I never caused her physical violence. I swear to you.’

He wonders what bearing it has on anything: the word of a criminal. But it is all he has, and as he speaks it, he hears his voice shake.

‘But you were convicted.’

‘Wrongfully,’ he states, his firmness veering dangerously close to aggression.

‘But if it wasn’t you, then who?’

‘I don’t know.’ His voice cracks. Tears come to his eyes. ‘I kept telling them about the noises I heard, about a possible intruder, but they weren’t interested. Instead they kept banging on about the row we’d had, asking me over and over again where I’d hidden the knife.’

‘The knife?’ Her eyes flare with interest.

‘Oh, yes. They never found it, you see? They tore the house apart looking for it, and the garden. They had search teams all over this park,’ he adds, his sweeping arm taking in the grass, the trees. ‘It never turned up, much is the pity.’ He tells her with conviction: ‘If they had found that weapon, I would have been in the clear. I’d have been exonerated. That’s the great mystery. It never showed up.’