Everything went well until they reached the outskirts of Leeds and were redirected for roadworks.

"Turn right," commanded the tom-tom. "Turn right."

When they didn't do as they were told, it seemed to get quite petulant.

"Recalculating."

Tilly could almost hear the sigh and see the rolling of the eyes as it calculated another route.

"Continue for two hundred yards and then turn right."

She could see it was trying to make them retrace their steps. ...