Your masterclass in layering begins and ends with one key item: a simple-as polo neck. This unsung hero, guaranteed to already exist in your wardrobe, is having a relevance renaissance thanks to fashion's obsession with the 70s (channel 'Diane Keaton as a Woody Allen protagonist' vibes when wearing yours). Here's how style-heavy girls are wearing theirs. Sing it: 'I'm in love with the polo...'