UK Conservative Leader David Cameron's disabled six-year-old son Ivan has died after taking ill overnight.
Ivan, who suffered from cerebral palsy and severe epilepsy and needed constant care, died in the early morning at St Mary's Hospital, Paddington in west London.
Today's Prime Minister's Questions has been suspended, Downing Street said.
Mr Cameron and his wife Samantha have two other children, five-year-old Nancy and three-year-old Arthur.
'David and Samantha would ask that their privacy is respected at this terribly difficult time,' they said in a statement.
Prime Minister Gordon Brown, whose infant daughter Jennifer Jane died from a brain haemorrhage in 2002, said he and his wife Sarah were very saddened by Ivan's death.
'The death of a child is a loss no parent should have to bear,' Mr Brown said.
'I know Ivan was a child who brought joy to all those who knew him and his was a life surrounded by love. The thoughts and prayers of the whole country are with David, Samantha and their family.'
Mr Cameron's experience of caring for Ivan has been seen as the driving force behind his promotion of 'Compassionate Conservatism', helping make the party electable again after a decade in the political wilderness.
The party is ahead in opinion polls with the most recent surveys predicting the Conservatives would be returned to government if an election were held now.
Before Mr Cameron was elected leader in December 2005, the Conservatives had struggled to shake off their image of being, in the words of one-time chairman Theresa May, the 'nasty party'.
Mr Cameron has made a priority of defending the state-funded National Health Service, praising it for all the help it had given his elder son.
'When your family relies on the NHS all the time -- day after day, night after night -- you know how precious it is,' he said.
