Show goes on ... Princess Beatrice, the Duchess of Cambridge and princes William and Harry enjoy the Jubilee Concert.

Dressed to impress ... Princess Beatrice, the Duchess of Cambridge and princes William and Harry enjoy the Jubilee Concert. Photo: Getty

The Duchess of Cambridge has gone from high-end to high street, wearing Whistles for the Diamond Jubilee concert.

Kate wowed the crowds during the Thames river pageant in a vibrant Alexander McQueen number, which drew rapturous applause from the fashion pack.

She continued the British theme for the concert, but this time opted for a dress by a more universal brand.

The Duchess of Cambridge brought a splash of vivid colour on an overcast day.

The Duchess of Cambridge brought a splash of vivid colour to proceedings on Sunday.

The duchess has been photographed wearing Whistles on a number of occasions and has become something of an ambassador for the label.

She matched her patterned blue and purple dress with a McQueen blazer.

As one of the most scrutinised women in the world, Kate has won much applause for her ability to combine off-the-peg purchases with items by top couturiers.

She is known to favour high street clothing lines such as Whistles, Reiss and Topshop.

But her prestige was cemented in fashion circles when she chose Sarah Burton, of McQueen, to design her wedding gown.

Princess Eugenie appeared to have taken a style leaf out of the Duchess of Cambridge's book, opting for a bright red dress.

Eugenie teamed her outfit with some rather more outlandish Gina shoes - adorned with the Union flag.

It is the second time the young royal has displayed such patriotism over the jubilee weekend.

She appeared at the Epsom Derby on Saturday with Union flags painted on her fingernails.

Her sister Beatrice went for one of Kate's go-to designers, stepping out in a peacock blue Erdem dress and Ferragamo blue wedges.

Red, white and blue have become something of a theme for the royals during the jubilee celebrations.

The Queen has been no exception, going for a white and silver Angela Kelly dress and hat during the boating extravaganza and picking blue for the races.

Beatrice and Eugenie also gave a nod to their grandmother, picking hats inspired by her wardrobe around the time of her coronation.

Insiders said the flash of pink in Eugenie's headwear was been inspired by the shade of "coronation pink" created in 1953.

PA