When I stepped inside Leroy’s flat, I thought there had been a fire. I parted the beaded curtain hanging in the doorway to his bedroom and failed to hide my shock. The walls of his South London home were stained black, with what looked like smoke and ash.

As I got closer, what I had assumed was soot was a thick blanket of furry mould, not an inch of the room spared. This was mould writ large, as if by design. My chest tightening, my breathing becoming more laboured, I asked Leroy how long his home had been like this.

“Months,” he replied. “I’ve told them, but they don’t do anything.”

It wasn’t just Leroy’s flat. The whole tower block in which he lived was plagued with leaks so severe they risked tenants’ lives. His neighbour, Fransoy, feared for her children’s lives in a home so damp that the walls fizzed with electricity. Light bulbs filled with water, slugs slid down her kitchen walls and sodden carpets squelched underfoot. The baby bath she once used to wash her two sons collected dirty water in her living room. She had begged for help, but none came.

I had arrived at Regina Road in Croydon after being given a tip-off about poor housing conditions. It was March 2021: lockdown laws still lingered, and some landlords were using them as an excuse not to make repairs to properties. That was meant to be my story – one of poor conditions and bad landlords. Instead I walked into some of the worst homes in Britain, stumbling upon a national scandal.