The stunning actress says it’s important to add colour below the chin as it adds ‘depth’ to the face and helps it to blend in with the rest of the body.

She said: ‘Always bronze underneath your jaw-line – it contours the face and adds depth. The bridge of the nose, cheekbones and temples are also essential.’

Sienna – who is famed for her laid-back style – also says it’s important to wear a fragrance everyday as it helps to change your mood.

She told vogue.com: ‘Fragrances have a nostalgic element to them and are an important part of who you are and how you present yourself. They are a sensory weapon and have the power to change your mood. I like the citrus notes of the BOSS Orange fragrances – they are young, fresh and uplifting.’

Sienna is often voted one of the world’s most beautiful women but says there’s only a couple of rituals she swears by.

She said: ‘I have facials by Linda Meredith and I get my hair coloured with Marie at Sally Hershberger when I am in New York or Leister at John Frieda if I am in London.’

The ‘Mama Do‘ singer admires the TV presenter’s quirky take on fashion and is desperate to buy the Mulberry bag named after the brunette beauty.

She said: ‘I really like what Alexa Chung wears. Those Mulberry bags named after Alexa are wicked – I don’t have one but I’m going to invest.’

Pixie also likes Sienna Miller’s fashion sense and was impressed with her latest collection for her label Twenty8Twelve, which she owns with sister Savannah.

She said: ‘Sienna Miller always looks good. I went to the Twenty8Twelve fashion show and the clothes were gorgeous.’

The 19-year-old beauty is known for her blonde locks and although she recently donned a dark wig for her ‘Gravity‘ music video, she would never become a permanent brunette.

She said: ‘It was really fun wearing that wig and I wore it out one night. But I definitely think I suit and prefer being blonde because that’s what I’ve grown up being and think it’s more me.’

Savannah – who now works with her actress sibling on fashion label Twenty8Twelve – admits she would put embarrassing clothes on her for fun.

She revealed: ‘I’d make her wear purple chiffon harem pants with an M+S bra I’d embroidered myself, and turn her into a little belly dancer.

‘Looking back, I can see that we’ve been working together on clothes in some capacity, for as long as I can remember.’

Discussing her collection – which is named after Sienna’s birthday – 31-year-old Savannah suggests the focus of the clothes has changed.

She said: ‘When Sienna and I first started, it was about designing clothes that we would want to wear.

‘Now, I feel the clothes are more about what our clients would want to buy, which is not always the same thing. I’ve learned to understand the customer, while remaining true to who we are.’

Savannah also admits to being surprised when she sees people wearing her designs.

She added to the Telegraph newspaper: ‘I will never forget wondering through Covent Garden one wintry day and seeing this girl wearing one of our poplin summer dresses with black tights and boots, and a chunky black cardigan.

‘She looked wonderful in a way I would never have expected; I love that people can take something of ours and make it their own.’