The archway stood gaping under a mechanical clock, with red bricks and an animal drive that moved to a stop. At lunchtime and teatime, and right round the block, the clock’s gears and its track pieces whirred as they spun up on top.

The children all gathered for the fieldtrip that was pending. A trip to the zoo they remembered her saying. It was so long ago, way back, they forgot they were waiting. The clock now began. The chiming had…