Prince William and Kate Middleton attend white-tie reception at Buckingham Palace

Kate Middleton wore Diana’s favourite tiara and an incredibly lavish embellished gown as she stepped out with the Royal Family for a white-tie reception.

Kate Middleton has stepped out looking dazzlingly regal in an off-white embellished gown and tiara for the Queen’s Diplomatic Reception at Buckingham Palace.

The event, attended by the Duke and Duchess of Cambridge, the Queen, and Prince Charles and Camilla, Duchess of Cornwall, was for members of the Diplomatic Corps.

There was clearly a colour theme. Photo: Victoria Jones/PA Wire

The Duchess of Cambridge looked especially regal. Photo: Victoria Jones/PA Wire

She accessorised her bejewelled gown with plenty of sparkling diamonds. Photo: Victoria Jones/PA Wire

Kate wore an elegant off-white gown with silver crystals, a slight cowl neck and cap sleeves for the white-tie affair.

She accessorised with pearl earrings and the stunning Cambridge Lover’s Knot tiara, which she’s worn on several occasions - and which was once favoured by Princess Diana.

Kate was glowing and appeared in good spirits. Photo: Victoria Jones/PA Wire

Earlier in the day, Prince William and Kate got right into the Christmas spirit, putting on an uncharacteristically affectionate display while throwing a festive party for RAF families at Kensington Palace.

The couple — both aged 36 — seemed in good spirits as they hosted the party for the families of deployed personnel from RAF Coningsby and RAF Marham.

The couple were all smiles. Photo: Karwai Tang/WireImage

The Duke and Duchess of Cambridge are generally pretty reserved with each other in public, but were clearly feeling particularly affectionate during the event.

Kate put a comforting arm around her husband as they spoke with their guests, and looked especially festive in a long red tartan skirt by Emilia Wickstead and a cashmere top by Scottish label Brora.

Kate looked stylish as ever. Photo: Karwai Tang/WireImage

While mingling with the RAF families, Kate thanked them for their sacrifices, telling the parents and children that she knows “how hard it feels” to have a loved one away from home for their job.

“When William served in the Falklands or in search and rescue, I know how that felt but I can’t imagine how it feels when your loved ones are away on active service — the absence of loved ones must be especially hard on Christmas.”

It was surely a welcome distraction amid a week of dramatic headlines surrounding Kate and her relationship with sister-in-law Meghan. Photo: Karwai Tang/WireImage

The Christmas event was supported by The Royal British Legion, marking the contributions serving personnel and their families daily.

It was particularly to thank them for their sacrifice of being apart during the festive period.

The party even included a visit from Santa Claus, as well as snowflakes blown into the sky as the Duke and Duchess walked in.

William puts a protective hand on Kate’s back. Photo: Karwai Tang/WireImage

Prince William also got into the spirit, learning how to make crackers with some of the children at the party.

The heir is Honorary Air Commandant of RAF Coningsby, Lincolnshire, which is home to Typhoon squadron.

And he couldn’t help but get involved after staff playfully threw a snowball at the future king — with William laughing as he tossed it back.

Other entertainment will include stocking decorating, snow globe decorating and creating Christmas party kits.

The couple themselves have big plans for Christmas Day, expecting to spend the day with the Queen at Sandringham.

- With The Sun