Prince William will attend a charity gala screening of The Hobbit: An Unexpected Journey in London by himself, leaving his ill wife Catherine at home alone.
The Duchess, 30, is in the early stages of pregnancy and has been suffering from acute morning sickness or hyperemesis gravidarum, which causes the sufferer to experience near constant nausea and vomiting.
After spending three days in hospital last week, Catherine again fell ill over the weekend and has been declared too sick to attend the star-studded gala tonight.
She will rest at their home in Kensington Palace for the foreseeable future until her symptoms pass.
The event, being held in London's Leicester Square tomorrow morning (Wednesday evening local time), is the official 65th Royal Film Performance and is the principle fundraiser for The Cinema and Television Benevolent Fund (CTBF), and William is said to be keen not to let down the organisers.
Before the film is screened, the prince will meet trustees and beneficiaries of the charity, the film makers and members of the cast.
William is currently on compassionate leave from his role as an RAF Search and Rescue pilot but is due back at work at RAF Valley towards the end of next week, leaving his wife in London if her condition persists.