I have a wardrobe full of navy blazers.

If you only have one jacket it should be a navy blazer. It doesn’t need to be double breasted with brass buttons like something from the yacht club. It could be in cotton, heavy canvas, or unstructured so it can look relaxed. But it’s a good basic to start a wardrobe with, you can dress it up or dress it down; it can take you anywhere.

Jeremy Hackett