Hair accessories can be tricky to get right, but Blake Lively shows exactly how it should be done.

The accessory is by Lorraine Schwartz, the woman behind Kim Kardashian's $2million 20.5 carat diamond engagement ring, and it works because the yellow-hue of the gems perfectly compliments Blake's golden hair colour and the floral detail on her Chanel Couture dress. Plus it's off-centre placement makes it less try-hard than if it had been positioned at the front.

Her hair has been loosely tonged and styled half-up, pinned in place with the brooch. The rest of her hair has been pulled into a dishevelled fishtail plait, with tendrils deliberately left loose.

If you want to try this hairstyle, use a little OSIS Dust It Mattifying Powder, £9.56 (lookfantastic.com), or dry shampoo on the mid-lengths and ends that you are pulling into the fishtail to give it that dry texture. Also, be sure to muss up the plait so it doesn't look too perfect - this hairstyle works because it looks undone and effortless, so keep that in mind.

See Blake's style file...

Check out other stars wearing jewellery-esque hair accessories...