The day before, Prince William had attended a charity tennis gala with the likes of Jude Law and Boris Becker, and he had spoken with guests about his wife's condition, telling them: "I don't know why they call it morning sickness – they should call it all-day and all-night sickness."
The next day he cancelled an appearance at British Military Tournament at Earl's Court, London, so he could care for the Duchess of Cambridge. He is expected to stay by her side until Thursday, as he had taken time off from his job as an RAF Search and Rescue Pilot to carry out several engagements.
The last one scheduled in is the royal premiere of Peter Jackson's fantasy epic The Hobbit on Wednesday evening. It's doubtful that Kate will attend, meaning she will likely not be seen in public until Christmas Day, when the royal family traditionally attend church together at Sandringham.
St James' Palace announced Sunday lunchtime that William would be "spending Sunday privately with the Duchess" instead of going to Earl's Court, adding: "It is well known that hyperemesis gravidarum often recurs and, until further notice, to allow the Duchess a degree of privacy during her pregnancy, we do not intend to offer regular condition checks or advise of routine developments associated with it."
Kate spent three nights at London's Edward VII Hospital last week being treated for the condition. She was discharged on Thursday morning and told reporters she was feeling "much better" as she headed home with her husband.
Although she worsened on Sunday, Kate's condition was not serious enough for her medical team to consider sending her back to hospital for treatment. She is being cared for by two doctors during her pregnancy – Jill Dando's former fiancé and the Queen's personal gynecologist Doctor Alan Farthing and his predecessor Marcus Setchell.
News of Kate's condition came as the row continued over the apparent suicide of a nurse who took a hoax call from two Australian DJs who pretended to be the Queen and Prince Charles. The hospital have suggested the blame lies with radio station 2Day FM for Jacintha Saldanha's death. Bosses of the company have said the hospital should examine their own role in the tragedy.
Radio hosts Mel Greig and Michael Christian went public for the first time since news of the nurse's death, describing themselves as "shattered, gutted and heartbroken" during a TV interview which was shown on Australian TV on Monday morning. "The first thing I asked was: 'Was she a mother?', said a clearly upset Mel during the chat with TV presenter Clare Brady in Sydney.