Pregnant Kate Middleton stuns in royal heirloom pearls previously worn by Princess Diana

Pregnant Kate Middleton, who is expecting her third child next April, was snapped last night arriving at a special dinner to celebrate the Queen and Prince Philip’s 70th wedding anniversary along with her husband Prince William and brother-in-law Prince Harry.

The mum-of-two chose her go-to second trimester evening dress for the intimate family occasion held at Windsor Castle. The Duchess has already been seen in her favourite black lace floor-length Diane von Furstenberg gown earlier this month to dress her baby bump for a royal event.

However, it was the Duchess of Cambridge’s accessories that really caught the public's eye as Kate sped past crowds in a car with Harry and William enroute to the special 70th wedding anniversary dinner.

The stunning pearl necklace that Kate wore for the evening was actually a special loan from the Queen herself, and has also been previously worn by the Duchess of Cambridge’s late mother-in-law, Princess Diana.

The Queen has owned the Four Row Japanese Pearl Choker since 1975, when she commissioned the piece of jewellery to be made from a set of beautiful pearls given to her by the Japanese government as a gift.

As pearls traditionally symbolise wisdom acquired through experience, they were an appropriate choice for the Queen to lend to Kate for the occasion, as the royal couple celebrated 70 years of married life together.

Kate wasn't the only member of the royal family to receive a special gift from the Queen yesterday. To mark their remarkable marriage milestone, the Queen made the Duke of Edinburgh a Knight Grand Cross of the Royal Victorian Order. This is a special honour bestowed by a monarch for services to the Sovereign, an appropriate Platinum Wedding Anniversary present for the man who the Queen has called 'my strength and stay' over the course of their lifetime together.