I first met Norman – not his real name – a couple of years before he killed himself. Coming home to my flat one evening, I heard a yelp at the other end of the dimly lit corridor. I approached the sound and found a short, middle-aged man, trying to unlock his front door. He was sweating.

The key wouldn’t turn – I tried too and failed. Then I noticed a look of sudden terror cross his face. “I’m mentally ill,” he said gently. “I’ve got a mental illness. I’m very frightened.”

“Well,” I said, in what I hoped was a reassuring tone, “don’t worry, OK? The guys at the front desk will be able to help you. They’ve got spare keys for most of these flats. Go and speak to them. Down in reception.”