Organisers had hoped Kate Middleton would be the stand-out guest on the night, before she fell victim to severe morning sickness.
Prince William attended the premiere on his own, saying his pregnant wife "would have loved to have been here".
After walking down the special "green carpet" which replaced the usual red for the night, William went inside to meet the cast and was presented with a Hobbit goodie bag to take home to Kate.
Meeting the film's stars, William joked with Australian actress Cate Blanchett, who revisits her role as the elf queen Galadriel from the Lord Of The Rings trilogy.
Cate looked stunning in a daring backless white dress.
Alongside her were The Office star Martin Freeman, who plays the title character, the Hobbit Bilbo Baggins and Ian McKellen, who reprises his role as the wizard Gandalf.