On the train on Friday night, a father and his toddler take their seat. The young boy is fascinated by the speed of the train, gazing out at the blur of buildings and lights that whizz past. Suddenly, without prompting, starts singing “Happy Birfday” (to his mummy) finishing with three muted Hip Hip Hoorays, after which he falls silent again and watches the world speed by.

A quick glance round the carriage and everyone has a little smile on their face; their weekend journey home suddenly made all the more bearable.