Andrew Grice: Don't write this man off. But questions now hang over his style of leadership

The gruelling past 12 months had already stripped away Tony Blair's aura of political invincibility. Suddenly, he is no longer invulnerable personally.

Although his heart scare came initially as a shock to the political world, on reflection it does not. Mr Blair has had an annus horribilis: the "Cheriegate" affair; the build-up to war in Iraq; the war itself and its messy aftermath; a divided, rebellious Labour Party; the death of David Kelly and the searchlight of the Hutton inquiry.

If "Teflon Tony" had finally lost his shine, then perhaps it was inevitable that, sooner or later, the image of a fit-looking prime minister and new father would follow suit.

Mr Blair has always tried hard to switch off from the pressures of the job. Despite his presidential style, he is less of a workaholic than Margaret Thatcher. His main escape routes are his family, weekends at Chequers and plenty of exercise - tennis, swimming and the gym.

Mr Blair has insisted on making time for his son Leo, yet the baby's unplanned arrival may have added to the pressures. Ironically, Robin Cook appeared yesterday to blame the birth of Leo for his removal from the Foreign Office in a 2001 reshuffle. In an interview in The Sunday Times, headlined "I don't blame Tony - it was baby Leo who finally did for me", Mr Cook said: "He was exhausted. He hadn't slept for two days. I felt sorry for the guy because he could hardly stay awake."

Close allies of Mr Blair admit that "ring-fencing" time has been harder than ever this year, and the Iraq conflict has piled on the pressure. There were few people with whom he could share the burden because it was seen by colleagues as "Tony's war". It could have cost him his premiership. The swift military success failed to relieve the strain, amid problems on the ground in Iraq and the failure to find weapons of mass destruction .

Last night's news will inevitably raise questions about Mr Blair's style of governing. The New Labour project was always a product of a handful of people. So it was no surprise that, on winning power, Mr Blair would adopt a top-down approach, with No 10 regularly interfering in Whitehall departments. In Mr Blair's eyes, this was the way to "get things done". Otherwise, he once told me, "You sit here pulling levers but nothing happens".

But in his second term, he has realised that "top down" has its limitations. Pausing for breath this summer, he acknowledged the need to treat his cabinet colleagues as grown-ups. So there have been two recent debates in the full Cabinet - on identity cards and pensions, issues that, under the traditional Blair style, would have been sorted by himself and the minister concerned, sometimes with Gordon Brown present.

It is far too soon to start writing off Mr Blair or dismissing the prospect of the third term he will need if he is to achieve his two main goals - reforming public services and taking Britain into the euro.

The timing of his scare, coming two days after the birth of Mr Brown's son once again highlights how the fates of the Prime Minister and his Chancellor are intertwined. Tension between the one-time soulmates over how to reach Mr Blair's two goals, which has simmered all year, boiled over at the Labour Party conference with Mr Brown, the leader-in-waiting, setting out his more traditional Labour agenda.

Over the weekend, allies of Mr Brown were already speaking of their hopes that fatherhood would allow the often hidden human side of their man to shine through, as it certainly did in his interview with reporters at Edinburgh Royal Infirmary. What a strange twist that, the following day, Mr Blair would visit a hospital for a very different purpose.