‘Decomposition is advanced. Thank goodness it’s not warm enough for the insects to be out in force yet, or this would be an even worse situation. As it is, my estimate of death won’t be terribly precise. I don’t know how long she spent in the water after passing, but I can tell you that her death would not have been immediate. There was little clotting around the wounds, so the water was warm and that kept the blood flowing.’

‘How long would she have suffered?’ Ava asked.

‘Difficult to say, but this isn’t the deepest of cuts. Keeping the ankles up above the buttocks would have kept the bleed more constant and her heart would have continued beating for possibly four hours, maybe longer. Eventually, her heart would have stopped. She might have gone into shock and died faster. I won’t be able to give you exact figures.’

‘Four hours? God Almighty!’ Ava said. ‘She’d have been screaming for help. I can’t believe no one heard her.’

‘The window was shut, the walls are thick – the property’s got to be a hundred years old – and there’s every chance people had music on or TVs playing. Or perhaps they were used to the sound of screams coming from this flat,’ Callanach suggested.

‘Could she have done this to herself, Ailsa?’ Ava asked.

‘She could easily have put the cable ties around her ankle and the taps, then run the bath. Logically, after that, she’d have had to have closed the cuffs around her left hand, made the two incisions on her inner arm, then got her right hand into the cuffs and snapped them shut.’

‘Which leaves the question – where’s the blade? Even if she’d thrown it out of the bath, it would still be somewhere in the bathroom,’ Callanach said, looking around. He shifted his body forwards to give himself the flexibility to turn, then opened the toilet lid. ‘One mystery solved. No blade, but the key to the handcuffs is at the bottom of the bowl.’

‘Don’t touch the water,’ Ailsa instructed. ‘If someone else was here recently, we might just get some cells from the seat or beneath the rim, possibly information about sexual diseases from any urine left in the bowl.’

Ava climbed past Ailsa to stare down into the toilet next to Callanach.

‘Looks like the right key to me. Small round barrel, ornate bow at the top. It’s obviously not meant for a door.’

‘Everyone out of here, please,’ Ailsa ordered. ‘I’ll need to get my team in to retrieve that and take samples.’

They left one by one, regrouping in the small lounge, where photos of cats and the late Mrs Hawksmith hung on the walls.