The Duchess effect

• ‘Sapphire’ Issa engagement dress

  Kate wore this stunning Issa ‘Sapphire’ dress on her engagement to Prince William back in November 2010. 24 hours later, the £385 dress had sold out at Harvey Nichols.

  Harvey Nichols’ buying director Averyl Oates said: 'Issa is one of our bestselling brands - since the announcement of the royal engagement we have been inundated with requests.'

  Budget imitations sprang up (and sold out) almost overnight too - including a £16 Tesco dress and £20 QVC copy of Kate’s sapphire engagement ring.

• Temperley Titan dress

  A month later, Kate was photographed wearing this black-embellished white chiffon silk dress at a charity event in Norfolk – Kate and Wills' first public outing since announcing their engagement.

  The £295 Temperley Titan dress had sold out just two days later.

  Kate is a big fan of the London-based label, choosing to wear their designs on a number of high profile occasions - including a day out at Wimbledon to watch Andy Murray play.

• Luisa Spagnoli red two-piece

  Kate wore this red skirt suit by Italian designer Luisa Spagnoli on a visit to St Andrews University, Scotland, where the couple first met.

  Soon after, stockists of the label - the Knightsbridge boutique Hollie de Keyser – were swamped with demand for the £335 jacket and £160 skirt, selling out in less than 24 hours.

  A spokesperson at Hollie said: 'Since Kate wore the suit, we have been inundated. We’ve now re-ordered 100 suits — £50,000 worth of stock.'

• Burberry trench coat

  Burberry has been enjoying something of a resurgence in recent years, with everyone from the Queen to Kate Moss wearing its designs – and the British label enjoyed another boost when the Duchess stepped out in this classic trench coat on a visit to Belfast last year.

  The flared hem design, £650, had sold out in every size within a day of Kate wearing it. Asda also reported a 300 per cent increase in sales of its purse-friendly £22 version.

• ‘Shola’ Reiss dress

  Reiss enjoyed another boost to its profile (and profits) when Kate wore its ‘Shola’ dress to meet the Obamas last year. Demand for the camel-coloured shift dress, £175, was so high it caused the retailer’s website to crash - twice.

  Reiss reported a 300 per cent increase in traffic to its site, posting on their Twitter page: 'Due to unprecedented demand, Shola mania has crashed our website! We are endeavouring to bring the Reiss brand back to you ASAP!'

• White ‘Peacock’ Reiss dress

  Just a month later, Kate wore another Reiss outfit – this time a stunning £194 ‘Peacock’ dress - to the Epsom Derby. Within hours of Kate’s appearance, an entrepreneurial owner of the same dress had posted it on eBay with an asking price of £625.

  Thanks to the ‘Duchess effect’ the British family-owned retailer, which has 114 shops in 14 countries, has seen its profits almost double in less than a year.

• Alice Temperley ‘Moriah’ dress

  And here is the white Alice Temperley dress Kate wore to watch Andy Murray play at Wimbledon. Within hours, the ‘Moriah’ dress, £795, had sold out online. 

  A statement on the fashion site, cSee Boutique, said: 'Unfortunately we've now sold out of the Moriah Dress but we have plenty of other Temperley London pieces in, so be sure to get them now before they disappear. You may not get the press attention that Kate does, but you'll definitely turn heads.'

• Brown Hobbs coat

  The Duchess again proved she’s a firm supporter of the high street by stepping out in a ‘Celeste’ flared coat from Hobbs. The brown belted coat sold out in under an hour after the Duchess wore it on Valentine’s Day.

  The coat with leather belt retailed for £369, before being reduced to £182 in the sale. Anyone who managed to buy one after Kate was spotted wearing it was very lucky indeed.

• Birdie shirt dress

  Later that same month, the Duchess wore this long-sleeved shirt dress to visit the Rose Hill Primary School in Oxford to support one her chosen charities, The Art Room.

  The Birdie shirt dress, £325, by Irish designer Orla Kiely (best known for her distinctive leaf prints on stationery and home wears) sold out in a matter of hours.

  Kate teamed the dress with a pair of Aquatalia brown ankle boots, one of her favourite footwear brands.   

   

• Coral jeans

  Asda were pleased to report an 88 per cent increase in sales of their £14 coral skinny jeans when Kate wore a pair of J Brand 811 coral jeans (£200) to play hockey with the UK’s Olympic team in London earlier this year.

  Brand director for Asda's George clothing line, Fiona Lambert, said: 'Now we have the royal seal of approval for coloured denim from Kate Middleton, we know this is going to be the hot trend this summer.'

• Next Up: Kate Middleton: a style retrospective

  Ever since she arrived on the scene in 2005, Prince William's lady, princess Catherine of Cambridge (though we still prefer Kate Middleton), ha

See also:

• Kate Middleton: a style retrospective