He didn’t wait. Before Mary could stop him, he brought up his foot and landed it squarely on the push-bar. The bolts banged back, the door swung open.

The narrow street was burning. Fire poured from the shattered windows in the building opposite. A line of cars, wreathed in thick orange flame and black smoke, were parked along the kerb, sitting on their steel rims, reduced to metal shells. The twisted shapes merging into the molten river of tarmac could only be bodies.

As the wall of heat drove them back, the taller man reached out, straining for the push-bar, to drag the door shut again. Instead, he fell into it, and it began to swing out wide.

The air itself seemed to tear in two.

Instead of fire, there was water.

A wave slapped through the open doorway, and a gust of wind blew into the smoke-filled corridor, dragging a spiral of soot outwards and away. It curled into a blue sky studded with clouds shaped like torn sheets, and a bird – a seagull – darted by at head-height. It wheeled back for a second look, before flapping once and soaring towards a tall headland of jagged black rocks.

The bottom of the cliff was strewn with boulders that extended out in a line as far as the door, and the sea washed over them, hissing and foaming, then drawing down with a rattling gurgle.

The light was bright and clean.

Another wave spilled across the threshold, and the tall man – not wearing a bandage, but a turban – struggled back in from where he’d fallen, half in and half out the door. The lower half of his orange boilersuit was already soaked and dark.

Mary looked behind her. It was the same corridor, the same smell of heat and burning, the same taste of smoke and ash, the same sound of failing steel and masonry. The same people she’d cheated death with, filthy, dirty, wild-eyed and desperate.

Then she tried to take in what was beyond the door: the land, the sea, the sky.

‘What the fuck have you done with London?’

She pulled the guy with the turban behind her, and hung out of the doorway, fingers clinging to the frame.

She felt the wind and the waves against her face. The spray was cold, a sudden shock after the heat, and she wiped her sleeve against her cheek. It came away wet.

Mary was afraid. The fire, the burning buildings, the cindered bodies: she’d been expecting that, had steeled herself to see it. But not this, this wide-open vista, nothing recognisable, no sign of brick or glass or plank or metal or dressed stone.

‘Mama? Mama, can you see this?’

Mama roused herself enough to sit up. She’d fared badly. Her feet and hands were raw and, where not raw, blistered.

‘Mary, girl. I see it. I see it.’

‘What do we do?’