No it's laughter. Well laughter yoga to be exact. "with the threat of terrorism hanging over our journeys, we need an injection of silliness to combat the climate of fear and anxiety". So we all pretend to laugh and it's infectious. Laughter therapy. Not that sort of nervous laughter that sometimes happens. You know the laughter when you've been stuck a bit too long in a tunnel and people think, what fun? This is hysterical. Ha, ha, ha. Anyone who starts laughing in those situations is likely to be carted off in a strait jacket.
But our laughter therapist, Ms Whitehead, continues with her Martin Luther King style wish:
"My dream is that for one day a week, the last carriage of every train becomes a place where you can look people in the eye and get together for a laugh. Perhaps London Underground would be up for it?"