Rear Window: Defenders of the faith: How Hal muddied the holy waters for Charles

IN THE summer of 1521, at the age of 30, the King of England published a book. Henry VIII may not be best remembered as a theologian, but that was the subject he chose to tackle, at considerable length, in Latin and in some style.

Assertio Septem Sacramentorum, or 'In Defence of the Seven Sacraments', was a counterblast to the Reformation writings of Martin Luther, upholding in forthright terms the authority of the papacy and the virtues of obedience.

Its style was polemical rather than academic - Luther was denounced as a 'venomous serpent' and a 'detestable trumpeter of pride' - and, perhaps in consequence, it became a bestseller. It went through 20 editions, prompted lively debate across Europe and even provoked its target to retaliate.

It was given its warmest reception of all in Rome. Henry sent Pope Leo X a personal copy bound in cloth of gold and adorned with dedicatory verses copied out in the royal hand. Leo read it immediately, marvelling aloud at Henry's erudition, and praising his arguments 'to the skies', Henry's ambassador recorded.

A few weeks later, in a Papal bull bursting with praise and affection, Leo formally conferred on the King of England the title Fidei Defensor - Defender of the Faith. The title is still used at coronations and in official royal documents, and - abbreviated to F D - it appears beside the monarch's head on British coinage.

Last week, however, the Prince of Wales suggested it needed amending. 'I would much rather see it as Defender of Faith, not the Faith, because it means just one particular interpretation of the Faith which I think is sometimes something that causes a great deal of a problem,' he told Jonathan Dimbleby in the ITV documentary on Wednesday.

For those with a taste for historical irony this particular plate is piled high: Leo's faith was, of course, Roman Catholic, but Prince Charles is a Protestant (like Luther); Henry, for all his oaths of obedience, later broke with Rome in order to divorce and re-marry, and added injury to insult by plundering the monasteries; more poignantly, one of the hottest themes in the Assertio was the indissolubility of marriage.

There are some, moreover, who have asked whether Henry really wrote the book at all. J J Scarisbrick, his biographer, admitted that this was a question that could never be answered conclusively. Although the picture of Bluff King Hal poring over theological tracts may seem incongruous, he had received a good education, was well-read and spoke several languages. Several witnesses testify, however, that he had help with the Assertio, from Thomas More among others.

Scarisbrick also points out that there was nothing spontaneous at all about the Pope's gift of a title. Henry had been envious for years of the 'Most Christian' King of France and the 'Catholic' King of Spain, and craved a sonorous religious label of his own.

'Defender of the Faith' was only one of several titles he had proposed to the Pope five years earlier, but the idea was rejected then. Even the Assertio barely did the trick; Leo dithered for some time and then ruled out the addition of Gloriosus or Fidelissimus which some cardinals had suggested.

Leo also conspicuously failed to authorise Henry to pass the title to his heirs. That honour was conferred on him years later, long after the break with Rome, by his own parliament. The Act of the King's Style, passed in 1543, declared that the words Fidei Defensor were 'united and annexed for ever to the imperial crown'.

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