"I am Britain's national sport that is not a sport. I require patience, not skill. I have invisible rules that everyone knows. Jump to the front of me at your peril. What am I?"

Answer: A Queue. Queuing is considered a quintessentially British cultural institution. Cutting into a queue is considered a serious social offence. The rules of queuing — no pushing, acknowledging who arrived first — are understood by everyone yet never written down.