"Right! There's the green man! Time to cross."
The Withenay family step out into the road. London traffic has reluctantly drawn to a halt, most of it behind the white line.
"Come on, children! Keep moving!"
The persistent beeps from the pedestrian light have ceased. I am aware one child lags behind. Mystified, I stop and stare at her.
"What on earth are you doing?"
My daughter is walking in a fixed fashion, one arm forward, the other back, and trying to make progress with legs in a similar position.
"I'm being the green man," she says.