Andrew Grice: How Cameron the politician was changed by Ivan

The discovery that his first child Ivan was severely disabled did much more than change the lifestyle of David Cameron. It also changed him as a person and a politician.

As political adviser to cabinet ministers Norman Lamont and Michael Howard, and later as director of corporate affairs at Carlton Communications, Mr Cameron's public school confidence sometimes extended to a touch of arrogance. Friends say that was knocked out of him by his and his wife Samantha's experience in bringing up Ivan.

At Carlton, former colleagues noticed a change in him after Ivan was born in 2002. One described him as a "different man" and "much less frivolous". Another said that whereas he had previously appeared "arrogant", Ivan's disability has been "a real leveller". His lifelong friend, the writer Giles Andreae, has said it had given the Tory leader "more humility".

Tory colleagues believe coping with Ivan's illness – and now his death — will give Mr Cameron a "sense of perspective" that many politicians lack. That might make it easier for him to cope with the setbacks he is bound to suffer and, one day, to cope with Enoch Powell's dictum that "all political careers end in failure".

One senior Tory official said yesterday: "David's priorities are very clear. He is a family man first and foremost. His time as leader has been a rollercoaster. His personal experience has made him a more rounded figure, better able to remain calm and cope in a crisis. A disappointing opinion poll is not going to wreck his day."

Mr Cameron himself has described the experience as "an eye-opener," saying: "Having a severely disabled son does bring you into contact with a lot of other elements of life. You do spend a lot of time in hospitals, you meet a lot of other parents and families in the same situation."

He and Samantha thought long and hard about whether he should talk publicly about Ivan. They decided that he was such a big and important part of their lives that it would be wrong not to.

They knew they would face criticism, and were proved right. Gordon Brown takes a different view. In a clear reference to his opposite number, he said last year that he did not believe politicians should use their children as "props".

Mr Cameron replied: "My view is very simple: I am asking people a massive thing to make me their prime minister and they need to know a little bit about you, what makes you tick. I am the father of young kids – and my family is very important. All you can do in public life is what you feel comfortable with. Some people criticise me for talking about Ivan but he is an important part of my life. My view is... do what you feel comfortable with and let people judge you." Aides say that, because of his position in public life, he can speak on behalf of thousands of other parents with disabled children who would not otherwise have a voice.

When he talks about his three top priorities being "NHS" – and focusing on his admiration for NHS staff, the need for special schools for the disabled, an end to the "postcode lottery" in help for carers and in favour of embryo research – he speaks from the heart and from personal experience.

Who can refuse to take him seriously on such issues, or say he doesn't know what he is talking about?

Personal tragedy has also moulded Mr Cameron's political views. It was no coincidence that one of his first acts on becoming Tory leader was to tear up a flagship policy in the 2005 manifesto Mr Howard had asked him to write – that a Tory Government would subsidise patients on NHS waiting lists if they opted for private treatment. The "patients' passport" had been seized on by Labour as evidence of the Tories' lack of commitment to the health service – and even a desire to privatise it.

Under Mr Cameron, the Tories have cuddled up to health professionals and now promise much less change than in other areas such as education. They would match Labour's budget for the NHS despite promising to spend less overall. When normal politics resumes it will be harder to portray the Opposition as a band of mad axemen ready to cut the NHS when it is led by a man who has often slept on hospital floors.

This can only help to inoculate him against charges by opponents that, as an Eton and Oxford man with a privileged upbringing, he is out of touch with the people whose country he aspires to lead.