The road from the station to the riverside was straight and wide. It and its wide pavement were not surfaced with tarmac but with scraped cement, giving them a temporary, construction-site feel. The drains, if there were any, had failed, and the gutter was a chain of giant, murky puddles. The lorries, which never ceased, sent up eruptions of filthy water, so our progress was halting. A shining stretch of cement would warn of a splash-zone, and we had to check if any vehicles were close before traversing it. I was reminded of the Nintendo platform games I played as a child: stop, wait for the swinging axe or angry ghost to pass, then jump the chasm. At the end of the road, where a wind turbine turned, was a compact constellation of flashing blue lights, twinkling and flowering in the drizzle.

‘We must be close,’ Pierce said, and I agreed when he said it, but again he was wrong. Perhaps it was the continual need to stop and wait for lorries to splash by, or the unfinished surface beneath our feet, or the overall hostility of the terrain, but a good deal of walking yielded little obvious progress. To our right, a collection of shiny new warehouses called Thames Gateway Park, then an online supermarket distribution centre, then the nerve centre of a popular brand of mass-produced bread. The supermarket’s delivery vans had fruit and vegetables printed on their sides; the bread giant’s lorries were decorated to resemble sliced loaves. The people we saw walking – three of them – shared characteristics: male, not white, hi-vis vests, an air of deep focus that suggested either tiredness or concentration on a task.

Two police cars were parked across the road ahead, one for each lane, front bumper to front bumper. Their lights strobed silently. Behind them, under the grey citadel of a cement plant, more emergency vehicles were parked: two police vans, an ambulance, two fire engines, and another fire appliance as big as an engine but not one, a mobile office or command vehicle. Yellow signs reading ROAD CLOSED stood in front of the police cars, strung with vibrating blue and white tape. Two police officers watched this frontier. They saw us coming from a distance and regarded us together as it became clear we were definitely approaching the tape rather than turning anywhere else. Words passed between them, certainly about us. As we drew closer, one of the officers walked – with deliberate, powerful slowness – to intercept us, gloved hands flexing, an expression of bored authority on his face. As soon as we were close enough to hear him, and there was no doubt we were going anywhere else, he spoke.

‘Road’s closed, gentlemen,’ he said, pointing in our direction, through us. ‘You’re going to have to go back the way you came.’

‘Can we just cut through?’ Pierce asked, with a casual air that I immediately envied. ‘We’re trying to get to the river.’