Lord and Lady Frederick Windsor were among the guests at a star-studded soiree to kick off festivities in London in the countdown to Christmas, with Sophie sharing a little known fact about the Princess of Wales's Christmas carol service.
Sophie, 44, and her husband Lord Frederick, 45, will be among the royal relatives at Kate's annual concert, which will take place at Westminster Abbey in London on 6 December.
And speaking at the Fayre of St James's Christmas charity event on Tuesday, the Sanditon star shared what she was most looking forward to at Kate's carol service, and hinted there's a family gathering after the event.
"Beautiful music and beautiful readings. And Hors d'Oeuvres," she said.
Sophie, who looked beautiful in a tartan Catherine Walker coat for the occasion, also revealed what's on her Christmas wish-list this year.
"I want to be taken for a Peking duck," before adding that her go-to venues are Imperial Treasure and Gouqi, both in Piccadilly.
The mum-of-two, who is patron of several charities, including Children's Surgery Foundation and Cure International, as well as an ambassador for Big Issue, also shared how she's giving back this year: "I hope I can give back, I'm trying to help all my wonderful charities."
Lord and Lady Frederick Windsor enjoyed an evening of readings, carols and performances at St James's Church, joining the likes of Richard E. Grant and Gemma Arterton.
The concert raises funds for the Quintessentially Foundation and its initiative The Firefly Project. The project focuses on children and young people battling the effects of poverty and disadvantage in London.
Sophie married banker Lord Frederick – who is the son of Prince and Princess Michael of Kent – in 2009.
The pair met on a night out after Frederick recognised Sophie from her role as Big Suze in Channel 4 comedy, Peep Show.
"We left two different parties and went for the same taxi," she previously recalled. "He said, 'You're Big Suze, I love you!' I laughed and asked the cab to take me somewhere. He pretended he was going to the same place, we shared the taxi and we've been together ever since."
The couple share two daughters, Maud and Isabella.