TODAY is the anniversary of the start of the English Civil War in 1642, which began when King Charles I raised his royal standard at Nottingham. The more I have studied Charles I, the more grateful I feel that it has not been my lot to live in the second quarter of the 17th century. There is a sad sense, as one looks at the late 1630s and '40s, of events' spinning out of control, and in different directions; so what might have resolved problems in Ireland would have exacerbated them in Scotland, and so on.

In England, the unhappy relationship between the Crown and Parliament was a significant factor in the descent into civil war. Much is made by Whig historians of the assertion of the divine right of kings by Charles I; but there was not a monarch in Europe who did not believe in the divine right to some extent.

Elizabeth I and James I believed in such a right, and they both had trouble with their Parliaments, but they were shrewder in their dealings than Charles I.

Another, and probably more significant, problem was religion. The year 1562, in which the Thirty-Nine Articles of Religion were published, was probably the high water mark of Calvinist influence in the Church of England. After this, there was a gradual divergence. In academic circles, there was something of a rediscovery of Patristics.

To read the Greek Fathers, however, is to be exposed to ecclesiology and sacramental theology, among other things. There was, consequently, a gradual clawing back of a more apostolic and thus Catholic understanding of Christianity. One might think of writers such as Hooker, Cosin, Andrewes, Taylor, and Thorndike.

Then there was the experiment in community life at Little Gidding, which Charles I visited three times. Nor must one forget Archbishop Laud's promotion of more reverent worship. Although it was not directly related, the spread of the theology known as Arminianism also undermined the Calvinistic influence.

This more Catholic view of Anglicanism, however, was only ever the vision of a minority of more educated people. The 16th and early 17th centuries saw the growth of more extreme Protestantism, notably Presbyterianism, and a whole host of smaller sects.

A religious clash was probably always going to happen, especially given the cultural and theological differences between the English and Scottish Reformations, and with the long shadows cast by the Thirty Years War on the Continent. It was the sad misfortune of Charles I to find himself king at a time of constitutional instability - in part, of his own making - and religious divergence.

WHILE researching Cosmo Gordon Lang in Lambeth Palace Library, I met some fascinating historians and writers, such as Professor Timothy Peters, a leading authority on porphyria. Professor Peters was researching the illness of George III, and has successfully demonstrated that the king did not have porphyria, but suffered from Recurrent Mania (Bipolar Disorder I).

He then turned his attention to James I, who, too, was alleged to have suffered from porphyria. Needless to say, he appears not have had it, either. James I had several very good doctors, who made detailed notes of his symptoms and illnesses. Professor Peters and his colleagues studied these, and then used computer-based diagnostics, as is currently done in specialist neurological practice.

This suggested that James I suffered from mild Lesch Nyhan disease. This condition is associated with Asperger's syndrome (high-functioning autism), which describes some of the features of King James.

Now, I am an archival church historian, not a medical historian; so I must be cautious. Lesch Nyhan disease is, like haemophilia, an X-chromosome disorder, and thus is not passed from father to son. Asperger's syndrome has a genetic component, however, and is often passed from father to son. This possibility is increased if the mother is depressed during her pregnancy.

We know that James I and his wife, Queen Anne of Denmark, did not enjoy a happy marriage. We further know that, in 1600, when she was five months pregnant with Charles, Anne became furious with James when he dismissed two of her ladies-in-waiting after the Gowrie Conspiracy. She stayed in bed for two days and refused to eat.

Depression during the queen's pregnancy, then, cannot be precluded, and seems quite possible. If further research shows that Charles I inherited Asperger's syndrome from James I, this insight would help enormously in our understanding of his life, and of the descent into civil war.

CHARLES I was an intelligent and well-educated man; but, at times, he saw things in black and white. Although he could be decisive, he could also be an irresolute ditherer. Some of his decisions were good; others were terrible, with tragic consequences.

In fairness, Charles I could also be a very kind man, especially to his servants, which in any age is an important indication of personality. The subject is worthy of further research.

If my hunch is correct, it reinforces a perception of Charles I as a tragic figure, trying to do his best for his subjects according to his lights, hampered by Asperger's syndrome, and a large dose of bad luck, frequently getting it wrong, as events spun out of his control.

One of the - not entirely respectable - games that historians sometimes play is called "What if . . ." What if, in 1936, Edward VIII had not abdicated and had married Mrs Simpson? What if, in 1914, Gavrilo Princip had failed to shoot Archduke Franz Ferdinand? Well, what would have happened in 1612 if Charles I's elder brother, Henry, Prince of Wales, had not contracted fatal typhoid? Prince Henry was clever, good-looking, a bit of a charmer - all the things that Charles I was not.

It is possible that, had he ascended the throne as Henry IX, there would have been no civil war. He might have avoided unnecessary wars with France and Spain, although he would probably have been tempted to interfere in the Palatinate. I have no doubt that he would have got on better with Parliament and with the Scots than his younger brother did.

My guess is, however, that there would have been a price to pay, and that price would have been the Church of England. Henry's formative boyhood years had been spent in Scotland, influenced by the Kirk. He was an advanced Protestant, who got on well with the Puritans, and was no enthusiast for Arminianism.

The English bishops were unpopular in the 1620s and '30s. It is not too much of a leap of the imagination to see Henry ditching episcopacy and turning the Church of England into an avowedly Calvinist, Presbyterian body. Some people would have been horrified, but most would have gone along with it. The Church of England would have become a footnote in a history book.

The fact that this did not happen is largely due to Charles I. He favoured the more Catholic and apostolic trend in Anglicanism. When he was 26, he wrote a private confession of his Christian faith. He began: "I am a Catholic Christian" - a remarkable statement for 1626. He believed in the veneration of the Blessed Virgin Mary and the saints, but did not seek their interces- sions.

While believing in liturgical and sacramental worship, he denied transubstantiation. He also rejected as "new fangles" the adoration of images, purgatory, indulgences, and papal infallibility.

In 1632, the king described his religious policy to the Lord Mayor of London:

It has also been our care since we came to the throne not only to defend the true faith that we profess, but also to maintain the Church and clergy in their proper jurisdiction, and dignity, and professions; and with all to encourage and enable our loving subjects, in all places to re-edify, repair and beautify their churches, that respect and outward appearance being a good effect and clear evidence of their zeal.

BRITISH kings and queens tend to go to church a great deal: it is part of their job. This churchgoing means more to some monarchs than others. Several historians have sought to trace Charles I's religious development. Canon John Fenton, the New Testament scholar, once said of Christianity: "You've got to feel it in your guts." Charles I came to feel Christianity - and, in particular, the Church of England - in his guts.

This meant that he was always going to clash with those of his subjects who felt other sorts of Christianity in their guts: Puritans and Presbyterians. After his imprisonment by Parliament, the king had several opportunities to save his life and regain his throne, but the price was always that he should consent to the abolition of the Church of England and its replacement by Presbyterianism.

The king refused. When all else had fallen away, he still believed that the Church of England was the purest form of Christianity, freed from later accretions, and in tune with the ancient Fathers. For this, he was prepared to die.

We Anglicans are very good at grumbling about the Church of England, sometimes with cause. We are not so good at recognising the Church's good points. On the whole, I suggest that the Church of England has been a good thing in our country's history over the past three-and-a-half centuries.

It has sought, with varying degrees of success, to be a religious home for a broad range of English people, and has helped to mould some of the good things in our national life and character.

We owe this, in no small respect, to Charles I's martyrdom, which helped to ensure the restoration of the Church of England with the restoration of the monarchy in 1660. The acceptance by Charles I of a Calvinist and Presbyterian Church would have resulted in the evolution of a very different England.

The Revd Dr Robert Beaken is Priest-in-Charge of Great Bardfield and Little Bardfield, in the diocese of Chelmsford, and the author of Cosmo Lang (I B Tauris, 2012).