The first door opened to a room with three children in it.

Older than the ones below, eight and ten and twelve by the look of them, seated at a table doing something structured, a lesson of some kind, books open in front of them and a staff member standing at the far wall who turned when I came in with the expression of someone whose day had just become something they hadn't prepared for.

"You can go," I said to her. "Marcus is in the corridor. Tell him I sent you."

She went.

The three children ...