‘Get off me, you lunatic!’ Sabih yelled between the cries and yelps of pain.

The road to the train station was quiet. A couple of cars had stopped, and the drivers were filming the violence on their phones, but no one was helping her partner. Harri recalled the moment she realized it was up to her, and she watched her past self step forward and extend her ASP – a telescopic baton that was intended to incapacitate. She swung at Munro and caught him behind the ear. He howled and dropped the knife, but reached for her again, so she fought him off with the ASP.

Adrenaline coursed through her and she remembered glancing over at Sabih, covered in his own blood. Was he dead?

Munro wouldn’t go down, which wasn’t surprising. Toxicology later found traces of PCP in his system. Munro managed to get to his feet and ran for the wall that separated the street from the embankment and railway tracks. He scrambled up and over the wall. She saw herself register the danger Munro now faced. There were train tracks down there.

‘Help him!’ Harri yelled at the nearest driver, pointing at Sabih. ‘Call an ambulance.’

The guy in the grey Vauxhall Astra nodded, but Harri was already moving. She wished she’d stayed, and it pained her to see her former self running across the pavement. But she knew if Munro wasn’t caught, he might hurt someone else. And if he strayed onto the tracks, he might hurt himself.

Harri sprinted to the wall and climbed over it to find a twelve-foot drop to the embankment. She made the jump without hesitating, which looked brave on camera, but Harri knew she’d been foolish. If she’d stayed with Sabih, her life wouldn’t have been ruined, and he might still be here. An unfortunate fall of the dominoes.

The railway tracks lay forty feet beneath street level, meaning none of the witnesses in their cars could see what happened next. The only person who knew the truth was the person filming from the railway bridge above them, the man whose video she’d been desperate to find.

On screen, Munro leaped from the shadows beneath the railway bridge and attacked her, and the two of them lost balance and tumbled down the embankment, which was constructed of fist-sized jagged stones. The fall was brutal and Harri remembered how sore she’d been for days afterwards.

She and Munro came to a halt by the tracks, and he staggered to his feet. She was so dazed she could hardly move, but she forced herself to her knees, ready to defend herself.

Horror flashed across her face as she realized the deep rattle and rumble she’d heard as they’d fallen hadn’t been the sound of their bodies clattering into the stones.

It was a train.

A fast freight train to London.

‘No! Alan! Look out!’ she cried, and she grabbed Munro’s T-shirt, but he resisted her attempt to save him and pulled himself free.