In the past, she has been seen with Prince Philip and body language expert Judi James commented on their relationship.
Prince Philip has not been out at many engagements since he officially retired in 2017.
When he has appeared with Kate, Judi claimed they seemed to have a good relationship.
She said: “These delightful poses suggest unexpectedly rich bonds between Kate and Prince Philip based on not just affection but also a shared sense of humour and fun.”
Judi drew on a particular outing when the two royals were seen together for one of the last times.
Prince Philip and Kate stood together on the balcony of Buckingham Palace at Trooping the Colour in 2017.
While they were surrounded by other royals, Kate and Prince Philip appeared to share a joke between themselves.
Judi continued: “Both royals tend to be fans of protocol at public events but Philip’s animated chat could have put them firmly on the naughty step, as judging from the poses of the rest of the group they are having a chat and a giggle during a fly-past.”
Over the years, she has also seemed to develop a good relationship with Prince Philip’s wife, Queen Elizabeth II, Judi added.
She stated: “The body language signals between the Queen and Kate currently suggest a very relaxed, warm and relatively easy-going friendship with both women enjoying the other’s company.
“While the Queen always appears to affirm the fact that, despite her age, she is not in any need of support or aid, she often looks happiest when her granddaughter-in-law and future Queen accompanies her or acts as co-host.
“Kate seems very adept at keeping a quiet eye on the Queen but without fussing.”