Alexa Chung, the face that launched a thousand Barbour jackets and Mulberry satchel bags, has a knack for turning pieces of clothing into hotter-than-hot cult items. 

The most recent piece to benefit from The Alexa Effect is the floral Topshop Unique Ottoline dress she wore to Topshop's London Fashion Week show back in February. 

Featuring a high neck, flared seventies sleeves, a short skater silhouette and a cool purple floral micro-print, the silk Topshop dress ticks pretty much every SS15 trend going - and a few AW15 trends too. 

The Topshop dress is clearly a favourite of Alexa's, since she was also spotted out and about in New York in it at the weekend with rumoured boyfriend Alexander Skarsgard.

Thanks to The Alexa Effect the dress sold out in under three hours when the first drop hit Topshop stores earlier this year. Topshop then met the demand by selling another load of the dresses a month later - which then also sold out. 

InStyle fashion director Arabella Greenhill thinks it's not just the Alexa endorsement made the dress such a sell-out. "It has that cool 1970s feel which is a huge trend for SS15, but there's also a high-neck Victoriana thing going on too which is a big look for autumn" she says, "plus it's versatile enough to wear to anything from a festival to a wedding."

This isn't the first high street piece to gain cult status. Remember the gold rush for that Marks and Spencer pink coat a few seasons ago? Or the year when every other woman was hankering after a bright pink Whistles pleated skirt? 

If you've missed out on Topshop's second drop of the dress, good news is you can still get your hands on some of that pretty purple micro print. Topshop are still selling this Ottoline blouse which has the same floral purple pattern and is a good option if you'd rather not bare your legs.

InStyle's Shopping Editor Robyn Kotze says "you can style it up for the rest of the summer - and into autumn - with some loose trousers or a denim midi skirt."

Or if purple's not your thing and you want something a little more neutral, try this high-necked Ottoline print blouse, which you can tuck into a high-waisted suede skirt for a quick hit of the Seventies trend.

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