The dashing young royal told guests at the special screening of the tale from Middle Earth that Kate would have "loved" to have attended the event. But the expectant mom has had to cancel a number of appearances while she battles severe morning sickness caused by hyperemesis gravidarum.
Tuxedoed William, 30, was the guest of honor at the royal premiere at the Odeon in London's Leicester Square, where he met filmmakers and some of the movie's stars, including Sir Ian McKellen and Cate Blanchett.
The cinema's general manager Tessa Street met William in the welcome line and asked about Kate. "I passed on my best wishes to Kate and he said, 'She would have loved to have been here if she could,' " Street told reporters.
The evening raised money for the Cinema and Television Benevolent Fund, and one of the fund's trustees Debbie Chalet also met the prince. "I said to William 'Thank you for taking the time to come and be here tonight,' because I'm sure he wants to be at home making sure Kate's okay."
Blanchett, who stars as Galadriel in The Hobbit, braved the chilly temperatures in a backless white Givenchy gown. Asked on the carpet how she was doing, she said, "I'm cold, but very excited."
Inside, just before the movie started, McKellen, who plays Gandalf in the movie, led the audience in sending best wishes to Kate.