I was very glad to get a reply from them as Princess Anne's office doesn't always reply.
The envelope is the usual from the British Royals.
The back of the envelope features Princess Anne's Coat of Arms.
Inside is a letter from Isabella Ward, Princess Anne's Office Secretary. It is pretty similar to past Christmas Replies from the couple.
The letter reads:
5th February 2020
Dear Miss Daly,
The Princess Royal and Vice Admiral Sir Time Laurance have asked me to thank you for your letter dated 21st December with its kind and supportive message for Christmas and the New Year. Her Royal Highness and Sir Tim are touched that you had thought to write to them again and send you their best wishes for the future.
Yours Sincerely,
Isabella Ward
Office Secretary to HRH The Princess Royal