The Duke and Duchess of Cambridge, who became parents to son George in July, arrived together in Range Rover with William behind the wheel.
Kate was looking particularly festive in a bright red dress, while she wore her hair down and loose in her usual trademark style.
William was wearing a smart blue shirt, tie and suit jacket. He had also popped on a pair of spectacles to drive his wife to the event.
It is unsure if Prince George was in the back of the couple's car - or even at the Royal lunch. Perhaps he's being looked after by his granny, Carole Middleton?
The Queen holds her Christmas lunch every year before the big day and the entire Royal family are invited.
Prince Charles was also spotted pulling into the Palace with Camilla, along with pregnant Zara Phillips - who is married to rugby player Mike Tindall.
Princess Beatrice was there, however sister Eugenie is currently in America studying.
Christmas is a busy time of year for the Royals, especially for Kate and Wills. Last week, they were spotted at the Natural History Museum for the premiere of David Attenborough's Natural History Museum Alive.
A fan of recycling her wardrobe, Kate wore her favourite lace Alice Temperley dress for the third time.
Take a look at what William and Kate's Christmas Day could be like in these spoof pictures by Alison Jackson!
Copyright: Alison Jackson/ Shloer