Yaa saw the girl outside, from her chair next to the window of the Lebanese restaurant on Edgeware Road, pacing. Young, pretty, black long hair pulled into a off-centre ponytail. Zebra-print trainers, grey tracksuit bottoms, big overcoat. Black polished nails. Headphones in, phone in hand. Just fashionable enough to make you think something wasn’t horribly wrong.

That was, until you saw how her right hand twisted anxious shapes in her coat pocket, and her left hand held a plastic cup. Her cheeks were too sallow, her face too gaunt, her neck too drawn. She wandered slowly up and down, almost convincing…