It’s 4.15 on a Thursday afternoon. The hall is buzzing with conversation. Around a table, adults and children burst into laughter as they wrestle with metallic tubing and googly eyes and their teenage helpers despair of ever creating the promised artefact. A toddler slaps green paint on to a huge sheet of card under the watchful eye of a granny (not sure if they’re related or not—it doesn’t really matter).
A five-year-old watches wide-eyed as an enthusiastic leader shows her how to bang...