Seizures grow steadily worse | The chamber was hushed, the emotion intense | Closeness of bond makes death of a disabled child more harrowing | Our leaders' need to grieve | Alpha Mummy: a role model for hardship I

When the certificate is written it will say the cause of death was acute abdominal failure at 6.30am on February 25, 2009, at St Mary’s Hospital in Paddington, West London.

The public record of a small boy stilled will tell nothing, though, of his last agonies, or of his parents’ final goodbyes. And yet the name it will bear – Ivan Reginald Ian Cameron – will indicate that the death of this six-year-old boy was not simply a personal tragedy.

Within weeks of his birth on April 8, 2002, David and Samantha Cameron knew that their first born was likely to die in childhood. That news – that Ivan had a severe, progressive neurological condition – was delivered at the John Radcliffe Hospital, Oxford.

It hit them “like a freight train”. Mr Cameron, who had been an MP for less than year, had never before had to cope with such personal devastation. He has spoken honestly about the couple’s subsequent battles with depression. In the months that followed, the Camerons’ faith and marriage were tested severely.

Their journey from that pit of despair – through long battles to win the right care for their son and to forge a family life as normal as possible – has set a new direction for Conservative politics, and may yet put Britain on a new course.

The couple made an early decision that they would not hide their son away. Mr Cameron, the MP for Witney, spoke in the Commons of his “magical child”, and he also wrote movingly on the subject.

“Ivan’s only self-conscious movements are to raise his eyebrows and to smile,” he wrote in a newspaper article in 2004. “And his smile – slightly crooked, sometimes accompanied by a little moan – can light up a room. It never fails to make me both happy and immensely proud of him.

“But with the smile comes epilepsy so powerful he can fit for an hour at a time, his small body contorted, often screaming in agony. And with the epilepsy comes cerebral palsy so severe that Ivan cannot move, sit up or hold on to anything or anybody. He cannot crawl, walk or talk and never will.”

The next year he told an interviewer: “He definitely recognises us. His eyes follow us very closely. Sometimes he smiles.”

When asked whether he and his wife thought it might be kinder to let their son die, he said: “It’s difficult. That is a conversation that we have quite often. What happens if he has terrible fits? . . . I’d rather not go into it.”

Such unflinching accounts made some uncomfortable, but Mr Cameron had little time for the squeamish – still less for those who accused him of exploiting his child’s condition.

The couple, who were used once to a life of relative privilege and luxury, were simply too immersed in the practicalities of their child to care much what others thought.

Their constant exposure to hospitals, respite nurses, social services and all the other apparatus of state-funded support wrought in Mr Cameron a deep and genuine respect for a service that his party had tended to treat with suspicion. Addressing the Tories during his first party conference as leader, he chose to confront head-on those who complained that Britain could not afford the NHS.

In a speech that Samantha Cameron helped to craft, he said: “I believe that the creation of the NHS is one of the greatest achievements of the 20th century. When your family relies on the NHS all the time – day after day, night after night – you really know just how precious it is.”

From the first day of his leadership he has been clear that an administration led by him would protect and nurture the NHS.

Gently but firmly, he has also put right those who rail against all “political correctness”. He, for one, is grateful that his son was not routinely called “spastic”.

There were no speeches from the Tory leader yesterday. It fell to the Prime Minister to bear testimony to Ivan’s power. “I know that in an all too brief life, he brought joy to all those around him and I know also that for all the days of his life, he was surrounded by his family’s love,” said Gordon Brown, who knows what it is to lose a child.

William Hague, speaking in place of his leader after Mr Brown decided to abandon Prime Minister’s Questions, hinted at the shock of Ivan’s death.

“His parents lived with the knowledge for a long time that he could die young, but this has made their loss no less heartbreaking,” he said.

On Tuesday when Mr Cameron bid goodnight to his small team at his Commons office and went home for one of his designated “family nights”, there was no hint of what lay ahead. Indeed, he was looking forward to the next day, when he thought that he would be photographed arriving at No 10 for the unveiling of a new portrait of Baroness Thatcher. That event was also cancelled.

Mr Cameron told a friend that Ivan had had a “very, very bad night”. The Tory leader and his wife went with their son to hospital in the early hours yesterday, arriving at 5.45am.

There had been scares before. Last April, two days after Ivan’s sixth birthday, Mr Cameron had rushed with him to hospital. On another occasion the boy’s hip had been broken in the course of a particularly violent episode.

Despite the diagnosis, Mr Cameron had allowed himself – once – to speculate publicly about what it might mean for his son to reach adulthood.

Speaking to The Times after a visit to a residential home for handicapped young adults, he said: “I can’t help but bring it back to Ivan and think what it will be like if and when he’s 18.”

In another interview he said that he was “philosophical” about the prospect of his son’s death. “You know that children like Ivan never make it to old age. You live by the day. But he doesn’t want to give up. This little person just wants to keep going.”

Mr Cameron drew inspiration from his son – as he drew inspiration from his father, who was born with a severely shortened leg. Ian Cameron, an enthusiastic sportsman and dancer, barely acknowledged that he was disabled and would not use a wheelchair until he was well into his 70s.

The same steel was on display in the photograph of the Tory leader’s family on his most recent Christmas card, in which Mr Cameron stares at Ivan with fierce love. The message of defiance was clear.

But in the early hours yesterday it appears that Ivan suffered a fatal spate of fits. The medical staff tried for 45 minutes to revive him but at 6.30am conceded defeat.

George Osborne, Mr Cameron’s closest ally and political friend, said of Ivan: “He quite regularly had seizures and problems and would have to go to hospital. He had such a seizure this morning and very sadly died shortly after admission to hospital.”

Ivan changed Mr Cameron, and Mr Cameron changed his party. Will that party – informed by the experience of what it is to rely so heavily on the NHS – in turn change Britain?

Ivan’s funeral will take place in Dean, Oxfordshire, the family’s constituency home, and Mr Cameron is not expected to return to work for two weeks. Normal politics were largely suspended yesterday. They will return to a course changed for ever by a young boy who could barely smile.

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