So Why Is Prudent Princess Kate Middleton Wearing A Cartier Necklace Worth £49K?

She's built a reputation as the Discount Duchess who would rather borrow her mother's high-street dress for her first public speech than invest in a new frock. But today Kate Middleton stepped out wearing a necklace worth an eye-watering £49,000. Say whaaa?

Arriving at the National Portrait Gallery this morning, Kate looked resplendent in a blue Stella McCartney dress blinged up by the statement necklace featuring three intertwined circles of pink, yellow and white gold. How fancy and utterly perfect for the Olympics-themed event, we mused. And so the hunt for the necklace began - is it another highstreet piece or perhaps a bargain from mega shopping mecca Bicester Village? No, no and no.

In fact, Grazia Daily has discovered the accessory is Cartier's Trinity necklace, which is available on cartier.com for £49,000. That's FOURTY NINE THOUSAND POUNDS. Considering her notorious 'prudent princess' ways, we're utterly flabbergasted that Kate would opt for such a luxury creation, despite it being undeniably stunning. What's more, the piece costs £19K MORE than six months' worth of her royal outfits! Prince Charles coughed up approximatley £30K for the Duchess' wardrobe during the first six months of being a royal, so we find it hard to believe that she would spend such a huge sum on one item.

Detective Grazia Daily contacted Cartier who are as surprised (and understandably delighted) as us, suggesting that the luxe jewellery brand didn't lend it to to the young royal for today's occasion. Meanwhile, Clarence House won't confirm a thing except to say: 'it's a piece of private jewellery'. Hmm, here are our theories...

1. Prince William brought it for his wife's 30th birthday

2. It was one of many Royal Wedding presents

3. Kate's new bestie Princess Charlene gave it to her when she visited the UK

4. The DoC decided to treat herself

5. Mum Carole, a fan of glitz, gifted it to her daughter

SO many possibilities! Tell us your verdict...