Sam McKnight’s Cool Girl Body is the hair product flat-haired girls need to know about

I’ve never met a Sam McKnight product I wasn’t besotted with. (Picture: Metro/Getty/Sarah Bradbury/Sam McKnight)

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As someone with famously fine, stubbornly flat hair, I’ve spent years chasing volume.

Not the big, Texan beauty-pageant kind. Just the sort of hair that doesn’t collapse by 11am afte...