When is it okay for men to go shirtless? And 46 other etiquette rules for during a heatwave

Summer etiquette: 47 essential rules – from sex to sunloungers to shopping in swimming trunks

When is it OK to go shirtless? What time can you start drinking on holiday? And can you ask a stranger to apply your sunscreen? Experts explain the behaviour that’s hot this summer – and what’s really, really not