Conservative leader David Cameron and his wife Samantha are mourning the loss of their eldest son Ivan. The six-year-old, who had cerebral palsy and epilepsy, became ill overnight and was taken to St Mary's hospital where he died early Wednesday.
A party spokesman said: "David and Samantha would ask that their privacy is respected at this terribly difficult time."
The politician, who has two other children, Nancy and Arthur, recently described Ivan as "wonderful".
Prime Minister Gordon Brown was one of the first to send condolences, saying the prayers of the country were with the family. "I know Ivan was a child who brought joy to all those who knew him and his was a life surrounded by love," he added.