The Duchess attended rehearsals as a guest of judge Craig Revel Horwood, who is a patron of the National Osteoporosis Society, a group that has Her Royal Highness as President.
She was welcomed at BBC Television Centre by BBC head of entertainment Katie Taylor and hosts Bruce Forsyth and Tess Daly. She was given a tour of the studio and introduced to the final seven celebrity contestants.
She watched the group rehearsals for a foxtrot to Adele's 'Rolling In The Deep' performed by pros Brendan Cole, Pasha Kovalev, Natalie Lowe and Katya Virshilas and then witnessed Harry Judd and Aliona Vilani's final practice for the quickstep on Saturday.
She was also given a tour of the costume department and studio gallery to meet the people who put the BBC show together every weekend.
Craig Revel Horwood said: "I'm delighted to have welcomed The Duchess to Strictly Come Dancing. Having got to know her through our charity work and having learnt what a fan of the series she is, it has been a pleasure to show her a sneak preview of this Saturday's show and some of the work which goes into making the series."
Strictly continues tomorrow night (November 26) at 7pm on BBC One.