When I was first elected to the House of Commons in 1966, I was a junior doctor at St Thomas’ hospital on the banks of the Thames directly opposite the Palace of Westminster. I specialised in neurology, which also involved undertaking some psychiatry.

For the following two years I crisscrossed Westminster Bridge, continuing to work on the chemistry of the brain in my laboratory while also attending parliament on the other side of the river. The neurologists and psy-chiatrists for whom I worked at St Thomas’ tended to treat a number of prominent politicians, and I saw the strains and stresses of political life within the confidential context of the doctor-patient relationship.

I helped treat a senior politician who had become addicted to alcohol and another who was severely depressed. I saw the pressures under which they lived and began to wonder how much of a factor stress played in their illnesses.

It was during those medical years that my interest began in how government decisions are taken, particularly at the highest level. The extent to which illness can affect the decision-making of heads of government, engendering folly, was an issue I faced quite directly on a number of occasions when I was foreign secretary. I was also fascinated by those leaders who were not ill but who developed what I have come to describe as hubris syndrome.

In ancient Greek drama, a hubristic career proceeds something like this: the hero wins glory and acclamation by achieving unwonted success against the odds. The experience then goes to his head: he begins to think himself capable of anything. This leads him into misinterpreting the reality around him and into making mistakes. Eventually he gets his comeup-pance and meets his nemesis, which destroys him.

The conduct of George W Bush and Tony Blair in deciding to go to war in Iraq five years ago and in handling its aftermath illustrates hubris syndrome.

There have, of course, been incompetent presidents and prime ministers before but Blair’s incompetence was of a very particular sort, and it was largely shared by Bush. It was triggered by three characteristic symptoms of hubris: excessive self-confidence, restlessness and inattention to detail. What drove both into hubris syndrome is not easy to quantify; there are some predisposing factors in their character and perhaps a few medical clues, but nothing definite.

My own personal experience of Blair is that his hubris started to develop in 1999 during the Kosovo crisis and built up over Sierra Leone and through the general election in 2001 until 9/11.

It was not present when I first discussed Iraq with him in 1998 in Downing Street. When I subsequently wrote to him arguing for a political strategy to help topple Saddam Hussein, he replied: “We are not working to bring down Saddam Hussein and his regime. It is not for us to say who should be President of Iraq, however much we might prefer to see a different government in Baghdad.” In December 1998, America and Britain launched a bombing campaign against Iraqi targets. Blair asked me to dinner at 10 Downing Street on the third evening of the bombing blitz. We discussed Iraq at some length. His mood was quite different from what it seems to have been two days earlier when, over dinner with his wife and two close friends, he was reported to be “distinctly nervous”.

I found him relaxed, almost laidback. There was no undue hyperactivity. He did not excuse himself to get an update on the attacks that had been launched and I found him cool, rational and anything but hubristic. He was ready to discuss the complexity of the relations between the Shi’ite majority and the Kurds and Sunnis in Iraq in detail.

My next conversation with Blair was during the Kosovo crisis when Nato was engaging in air attacks on Serbia in April 1999. He unexpectedly rang me wanting a long and detailed talk about his anxieties over the deteriorating situation.

I mentioned that I was speaking from Berlin on an open line. He laughed and said he wanted anyone listening to know about his anxieties. He was surprisingly frank and we had an animated discussion. I sensed, however, for the first time a note of exaltation in his voice.

Kosovo was his first test in a big international crisis and unmistakable signs of hubristic attitudes were beginning to emerge. Visiting refugee camps he was hailed as a hero. At one stage, President Bill Clinton angrily told Blair to “pull himself together” and halt “domestic grandstanding”.

He was starting to display excessive pride in his own judgments. Clinton’s aides mocked Blair’s Churchillian tone. One official who frequently saw him said: “Tony is doing too much, he’s overdoing it and he’s overplaying his hand.” One of Clinton’s aides suggested Blair “was sprinkling too much adrenaline on his cornflakes”.

It is worth noting how often this hormone is referred to when people discuss manic or hubristic behaviour. But if there is any linkage it is a complex one embraced within the two-factor theory of emotion, where the adrenaline may produce a physiological arousal but there also needs to be a thought process or cognition to interpret the meaning of this arousal.

In September 2001, his response to the 9/11 attacks in New York and Washington was again very personalised. Both Bush and Blair claimed that the challenges they faced were unparalleled in human history. Their language began to take on the ring of zealotry: nuance and qualification became rarer; certainty and simplicity became ever more dominant.

Blair’s own particular form of hubris was his need to put himself visibly at the centre of events. The world after 9/11 provided him with endless opportunities for eye-catching initiatives. Pursuing a frenetic schedule, he held 54 meetings with foreign leaders, and travelled more than 40,000 miles on some 31 separate flights.

He tried to keep up the same pace through 2002 and much of 2003. Bush, by contrast, insisted on having enough time to sleep, and appeared less frenzied and more controlled.

We now know from leaked papers that Blair seems to have ignored the concerns of his officials over the planning for the war in Iraq, particularly for the aftermath.

A senior official recalls that when Blair was advised about the difficulties ahead, he would respond: “You are Neville Chamberlain, I am Winston Churchill and Saddam is Hitler.” It is difficult to conduct a serious dialogue with a leader thinking in this emotional and simplistic way.

A secret memorandum dated July 23, 2002, published in The Sunday Times, described a meeting on Iraq at which, inter alia, the chief of the defence staff, Admiral Sir Michael Boyce, told Blair that the military “were continuing to ask lots of questions”. Yet in conversation with me over dinner the day after this meeting, Blair was dismissive of any difficulties and trying to give me the impression that it was all being dealt with. This was not ordinary incompetence, it was hubristic incompetence. He was becoming immune to all arguments about the practical difficulties that might ensue.

What was especially noticeable was that, while he had been ready at dinner in 1998 to explore the complex internal politics of Iraq, he was now totally unwilling to have any detailed discussion about the consequences of invading. There were no problems, he seemed to believe, that could not be solved and were not being solved. I was left with the strong impression that Blair was a very different man from the one I had met over dinner 3½ years earlier. Several clear symptoms of hubris syndrome were now manifest. Besides the firm belief in his purpose, which I discussed afterwards driving home with my wife, there was a total confidence in himself and as a new feature a restless, hyperactive manner. As my wife said afterwards, he was messianic.

In the wake of the invasion of Iraq in March 2003 it would become ever more obvious that Blair had covered up the true nature of an illness he was suffering from. It was compatible with hubris syndrome that he should have embarked on a course of deception.

On Sunday, October 19, 2003, it was leaked to the press that he had attended Stoke Mandeville hospital near Chequers. Only later was this news officially confirmed by 10 Downing Street. Blair was then transferred to west London’s Ham-mersmith hospital to be treated, allegedly, for only a commonplace increase in his heartbeat.

Later that night, it was stated that he had never suffered from heart problems before. But it was also announced that he had had cardiac shock treatment, or cardioversion.

In as much as a medical condition was named at all, it was referred to as a “supra-ventricular tachycardia”, a term which in this context was ambiguous.

It meant either a relatively benign arrhythmia (an abnormality of the heartbeat), or something from a range of arrhythmias not so benign such as atrial fibrillation and atrial flutter, caused when the arrhythmia has its origins above the ventricles.

Some cardiologists were surprised that the prime minister had had cardioversion for what was apparently a mere supra-ventricular tachycardia and felt his real condition was likely to be atrial flutter.

The suspicion that there might be something more serious about Blair’s medical condition was strengthened by Bill Clinton’s blurting out: “I’ve known about this for a long time. He told me about it quite a few years ago.”

This was denied by both No 10 and Blair himself. Downing Street said: “The prime minister did not have, and had never had, a heart condition, nor had he had this complaint before.”

Yet we now know from the diary of a senior cabinet minister, David Blunkett, that two days after treatment: “Tony told me when I spoke to him on the telephone that he had had the heart problem, on and off, for 15 years, but this time he had to go into hospital, which was why it became public knowledge.”

At the annual diplomatic reception at Buckingham Palace a month after his visit to hospital, I had another talk with Blair about Iraq. He insisted on us sitting down together for a serious discussion in the ballroom and ignoring for a time the foreign diplomats circulating around.

This was a very different Tony Blair from the messianic leader I had talked to over dinner in July 2002. He was far less sure of himself and he appeared somewhat chastened by events: the inability to find any weapons of mass destruction in Iraq was clearly troubling him. I felt rather sorry for him and tried to cheer him up. But I was, by then, fearful of a debacle in Iraq and annoyed at his incompetence.

I noted down afterwards that he was clearly very worried and that he had aged very much, deep in his face, the contours of which seemed to have changed. He also appeared to have lost weight.

I wondered then if his heart condition had been brought on by increased activity in his thyroid gland, which would have explained his weight loss and hyperactivity, but there is no evidence that thyro-toxicosis was diagnosed.

Nearly a year later, Blair went into hospital as an outpatient for a procedure known as a catheter ablation, treatment for his irregular heartbeat. This time the hospital admitted he had atrial flutter. But an official statement issued by the prime minister’s own cardiologist still avoided any reference to a specific heart condition.

So at a time when the Iraq crisis needed new policies and fresh thinking, Britain had a prime minister in office hiding his illness, denying the facts and pretending to be fit and well.

There has been speculation that for some years Blair had been on betablocking drugs for his heart arrhythmia. I asked a scientist with long experience of these drugs whether he knew of any long-term side effects that might predispose Blair to hubris in that the normal alerting mechanism in the body to strain and stress was being damped down. He claimed to have had a similar request from the Foreign Office about Saddam Hussein!

One doctor wrote to me speculating on the medication Blair might have been taking, that having watched him on television for many years, he had noticed how his receding hairline had moved forward and then, after his announcement of his treatment for tachycardia, had moved back again.

The doctor wondered whether Blair might have been taking Regaine for hair growth, which has a recorded side effect of triggering tachycardias. He postulated that when the doctors realised he was on Regaine, they told him to stop using it.

Whatever the truth, the likelihood is that it is Blair’s personality rather than his heart condition that has contributed to his developing hubris syndrome.

Several personality traits stand out very obviously. First, his early passion was not politics but performing. Actor-politicians tend to be especially narcissistic – which makes the hero role almost irresistible.

A second trait concerns his view of himself, in that he thinks he is always good. Someone who believes they cannot act badly will also believe that they cannot lie, so shading the truth can easily become a habit.

Linked to this is the nature of Blair’s religious beliefs and the particular way he sees his relationship with God. In a television interview two years ago, he said, in relation to Iraq: “If you have faith about these things then you realise that judgment is made by other people. If you believe in God, it’s made by God as well.”

The implication is that the accountability that really matters to Blair is not to the electorate but to God. If, however, he is already convinced of his own goodness, that accountability is not constraining as it would be to the believer aware of his own capacity to sin. The belief in God becomes a spur to hubris rather than a constraint on it.

No scientific explanation for hubris syndrome has yet been found and no such explanation may ever be found. However, watching the changes in the new sciences of the mind in my lifetime, as a former neurologist and politician, I believe they may ultimately provide an explanation of why some leaders succumb to hubris syndrome while others do not.

It may be that it never has a medical cure or even a proven medical causation, but it is becoming ever clearer that, as much as or even more than conventional illness, it is a great menace to the quality of leadership and the proper government of our world.

© David Owen 2008

Extracted from In Sickness and in Power: Illness in Heads of Government During the Last 100 Years, by David Owen, to be published by Methuen on April 10 at £25. Copies can be ordered for £22.50, including postage, from The Sunday Times BooksFirst on 0870 165 8585

Explore Books

• Book Extracts

• Book Reviews

• Books Group

Times Recommends

• The Gone-Away World by Nick Harkaway
• Burning is too good for them
• Strange Fruit: Why Both Sides Are Wrong in the Race Debate by Kenan Malik