The late Jessica Berens, the journalist, author, charity worker and writer-in-residence at the notoriously tough Dartmoor Prison, who died earlier this year aged 59, was a heroine of mine. She remembers a scary moment when she was walking along a passage in the prison with a lifer. Suddenly, the lights went off. “Don’t worry,” he said. “I trust you.”

The story came to mind this week when I was struggling to lug my bike up the stairs of the Golden Jubilee footbridge across the Thames, near Embankment, not realising there was a lift. I looked up and saw a powerfully built young man bounding along the pavement towards me. He was wearing a grubby grey hoodie, and I couldn’t make out his face. Oh no, I thought, trying to work out how I could grab my bag, phone and wallet from the bike’s yellow wicker basket without letting go of its frame or falling down the stairs. “That looks tricky,” he laughed. “Can I give you a hand with that bike?”

Both stories got me pondering on the kind of thinking traps we can fall into. First, how easy it is to live in a state of high alertness, with a highly developed fight-or-flight response. And, second, which is related, how often we then construct narratives about the intentions of those around us – often negative ones – falling into the mistake of imagining we can read the minds of others.