There are multiple reasons one particular £20 blue-and-white striped shirt is amongst Zara's current best sellers. It's versatile and smart. It's affordable. It's tapping into fashion's ongoing love affair with all things related to button-downs and blouses. It's very spring-ready. It's flattering on everyone. It's something you'll find in designer circles just as easily as you will on the high street… Those are enough to justify its mass popularity, but more than all the above, the truth is almost every girl under the sun can look good in a blue-and-white button-down.