Sienna Miller's stylist reveals how to get her 'perfectly tousled hair' – and the secret is this £27 mist

Drop everything - Sienna Miller’s hairstylist has just revealed the secret product he uses to create her 'perfectly imperfect' tousled waves – and we've never added to basket so quickly.

Sienna Miller’s go-to boho waves look like such an effortless hairstyle - But, as anyone whose ever tried to recreate them will tell you, it's harder than it looks to get that perfectly imperfect and tousled look.

Thankfully, her hairstylist Sam McKnight has now peeled back the curtain and revealed exactly how to create the stunning, elevated casual style on any and all hair types. Whether you have fine hair and are trying to figure out how to get thicker-looking hair, or you're trying to get your curls to drop into those envious laid-back waves, it's good news all round - all you need is one product.

Shop Sienna Miller's Texture Hair Mist

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Aptly named the 'Cool Girl' hair mist, this dry texturising spray is designed to be spritzed onto dry hair and simply needs to be worked in by scrunching and tousling the hair. 'Mess it up,' the instructions read, with the tousled and 'done, undone’ look encouraging you to really break down whatever style you've cajoled your hair into in order to get Sienna's look.

As an added bonus, the spray is infused with a perfume created by expert perfumer Lyn Harris. Spritzing it onto your strands, you'll immediately smell the hit of fresh, floral and subtle spices that are created by the addition of green leaf, herbs, watery flowers, pepper, frankincense, cedar and juniper wood to the formula - it's a real treat for the senses.

While you can spray the texturiser onto your natural, unstyled hair to get a dishevelled, effortlessly cool look, there are some tips and tricks that Sam McKnight has to getting Sienna's exact style on any hair type.

He told British Vogue, "Truly tousled hair is cool and effortless, it doesn’t try too hard. So creating a texture in hair that feels natural and not over-styled is key – whether it’s created with styling tools, or your natural hair is enhanced with styling products, it’s all about movement."

So forget strong-hold hairsprays and slick hair waxes. Just focus on the basics and try to be 'imperfect' about your styling approach. If you have straight hair, McKnight suggests giving it a little wave with a curling tong. "Try waving it in different directions for that signature cool girl hair texture," he says.

If you have curlier hair and struggle to get a loose, wave, he recommends stretching out each curl gently with a hairdryer for a more relaxed feel. Then, go in with the texture spray.

“Your styling products should both enhance and control your look," he adds. “If your hair needs more body and texture a dry texturiser should be your go-to."