For most of his life Charles V was by far the most powerful man in the civilised world. Born in Ghent in 1500 and consequently the youngest of our four princes, he was the grandson of the Emperor Maximilian, the son of Philip the Handsome of Austria and Joanna the Mad of Aragon and Castile. He had inherited neither of his parents’ primary attributes. His appearance was unattractive and ungainly, with the characteristically immense Habsburg chin and protruding lower lip; and he was fully aware of the fact. He used to say with a smile that he couldn’t help being ugly, but that, as artists usually painted him uglier than he was, strangers on seeing him for the first time were agreeably disappointed. He suffered also from an appalling stammer. He was serious, and deeply religious; one never gets the feeling that he enjoyed his monarchy in the way that Francis and Henry did – indeed it is doubtful whether the idea of doing so ever entered his head. Not for him were the roistering and the feasting, the glowing velvets and the brocades; at least in his youth, he ate sparingly and usually alone, and while there were obviously occasions when he was obliged to dress richly – as when Titian first painted him at the age of thirty-three – he always appears vaguely uncomfortable; it is only in the master’s third and last portrait, painted fifteen years later, that he looks at his ease. He is then dressed entirely in black, with the Golden Fleece around his neck providing the only touch of brilliance.

Apart from his religion, his life was dominated, as it had to be, by politics. A little less intelligent and a lot less cultivated than Henry or Francis, he was far more industrious than either. Unlike them, he had no real interest in literature: most serious books were still written in Latin, and his mastery of the language, like that of Francis, was always surprisingly weak. As a boy he had devoured the Mémoires of Olivier de la Marche, a fifteenth-century member of the Burgundian court whose surprisingly salacious tales of chivalry and derring-do on the part of former dukes had enjoyed immense success in court circles; later in his life, what little spare time he possessed was devoted to music, for which he had a lifelong passion. He played the spinet, the flute and several other instruments; he sang, we are told, like an angel.

His inheritance was greater than that of any European ruler in history. It began with the Burgundian Low Countries, which had come to him through his grandmother Mary of Burgundy and where he spent his childhood. Since both his parents had left for Spain when he was still a baby, he was put under the guardianship of Margaret of York, the childless widow of Duke Charles the Bold of Burgundy and the sister of the English kings Edward IV and Richard III; after her death in 1503 his upbringing was entrusted to his father’s sister Margaret of Austria – also childless after two marriages – who ruled as Regent until, at fifteen, he took over the reins himself. His father Philip was long dead; his mother Joanna, though already hopelessly insane, was still technically Queen of Castile, with her father, Ferdinand of Aragon, acting as Regent; but shortly after Ferdinand’s death in 1516 – rumoured to have been due to dropsy, brought on by an aphrodisiac given him by his second wife, Germaine of Foix, in the hope of begetting a child – Charles was proclaimed King not only of Aragon and Castile, but also of Naples, Sicily and Sardinia. Then, in January 1519, his grandfather Maximilian died of a massive stroke at the age of fifty-nine. Since the Empire remained elective, the succession of his grandson was by no means a foregone conclusion; Charles, however, was determined to secure it at any cost – if only to prevent it from falling into the hands of Francis, who was initially supported by the reigning Pope, Leo X. From his point of view the election of Francis would have been a catastrophe; it would have spelt the end of his hopes of regaining Burgundy, and might even have called into question the hereditary Habsburg lands in Germany and Austria. Fortunately for Charles, however, the German electors hated the idea of a French Emperor almost as much as he did himself; the Fuggers – that hugely rich and influential banking family from Augsburg – lined as many pockets as was necessary; and Charles was elected – unanimously – Holy Roman Emperor. The whole operation probably cost him rather more than half a million gold florins. He was to remain in debt for the rest of his life.

Maximilian had never thought much of him. If it was not for the boy’s love of hunting, he used to say, he would have questioned his parentage. He made no secret of the fact that he vastly preferred Charles’s younger brother Ferdinand, who with his easy ways, charm and gregariousness was by a long way the more attractive of the two; he was also much better-looking. It may well be, indeed, that his grandfather’s disapproval lay at the root of the difficulties that Charles always had with his German subjects, in whose language he was never really happy. His first language had been French, and since his childhood he had also spoken fluent Flemish – though this was not at the time considered a ‘polite’ language. When he first went to Spain at the age of seventeen to claim his inheritance, he still possessed not a word of Spanish – though it was rapidly to become his second tongue. ‘The divine language’ he called it, and he used it always when speaking or writing to his wife and children (though he wrote to his brother’s family in French). He is frequently quoted as saying that he spoke French to his friends, German to his horses, Italian to his mistresses and Spanish to God.

Strange as it may seem, Charles had spent all his early youth in Flanders; never once had he visited the old Habsburg lands. Now, in addition to his already vast domains, there devolved on him with his election all the old patrimony of the Habsburgs, comprising most of modern Austria, Germany and Switzerland. Milan, Bohemia and western Hungary were to follow a little later. For a man whom most people believed – mistakenly, as it turned out – to be of modest talents and frankly mediocre abilities, here was an inheritance indeed. Sensibly enough, he soon decided to entrust the central European part of the Empire to his brother the Archduke Ferdinand, despite the fact that the Archduke had been born and brought up in Spain and never set foot in the old Empire until his eighteenth year. In 1521 he married Ferdinand to Anne, the sister of King Louis of Hungary; and in the following year Louis married his and Ferdinand’s sister Mary. Thus, if Louis were to die without issue, the Empire would be extended to the frontiers of the Slavonic world, and Charles’s position vis-à-vis the Ottoman threat would be at least to some degree strengthened. Even so, his life involved almost constant travelling; and travelling in the early sixteenth century, even if one was an Emperor, was an uncomfortable and exhausting business. Backwards and forwards he went, principally between Spain and the Low Countries, but also to Italy, France, England and even north Africa. He travelled up and down the Rhine, through Württemberg, Bavaria and Austria. All in all, he probably spent several years of his life on the road, and several months at sea.

Soon after his election, his vast dominions were still further increased. In the space of a single decade Hernán Cortés defeated the Aztec Empire of Mexico and Francisco Pizarro the Inca Empire of Peru. Within a year or two, Spanish galleons were bringing untold wealth back across the Atlantic. These successes, combined with Ferdinand Magellan’s circumnavigation of the world in 1522 – Magellan was Portuguese, but Charles had provided all five of his ships and most of the finance – left the Emperor in no doubt about his destiny: it was clear that he had been divinely ordained to be the leader of Christendom.

Charles’s election as Emperor brought Spain into the heart of Europe. Spanish soldiers were henceforth to fight in Germany and the Netherlands; Spanish writers and philosophers imbued themselves with the new humanism of Erasmus and his followers. At the same time Spain was acutely conscious of being the one firm rock of the True Faith, its chief defence against the vile Protestant heresies springing up in the north. The election also – and this was perhaps still more important – resulted in the polarisation of continental Europe. France was now trapped as in a vice, virtually encircled by the Empire; conversely, Charles found himself sovereign of a divided dominion, its two parts cut off from each other by a hostile state between them. The result was inevitable: a lifelong struggle between the two men for dominance in Europe and mastery of the western Mediterranean.

The new Emperor had two principal ambitions. The first involved the Duchy of Burgundy. By the accession in 1467 of Charles the Bold, the last of its four great Dukes, Burgundy had become, with Venice, the most powerful state on the continent of Europe. True, the Duke was a vassal, who owed homage to the King of France for his traditional Duchy together with Flanders and Artois, and to the Emperor for the remainder; but his court was more splendid than either of theirs, and when his contemporaries called him ‘the Grand Duke of the West’, it seemed no more than his due. Duke Charles, however, though undoubtedly bold, had also been dangerously over-ambitious. He had foolishly set himself up against France, at whose hands he had suffered a whole series of defeats before being killed at the Battle of Nancy in 1477. Most of his lands had subsequently reverted to the French crown. The Emperor, as the grandson of Mary of Burgundy and great-grandson of Charles the Bold, was deeply conscious of his Burgundian blood, and was determined to restore the Duchy to what it had been only a quarter of a century before his birth, serving also as an invaluable buffer state between France and Germany. As late as 1548 we find him, in his political testament, charging his son Philip never to abandon the claim to nuestra patria – ‘our country’.

His second ambition was still only a dream; yet it was a dream that he believed might easily come to pass. He longed to win back the ancient Empire of the East. Old men were still alive who remembered that dreadful day in 1453 when Constantinople had fallen to the young Sultan Mehmet II – and the Byzantine Empire, after more than eleven centuries, had come to an end. Throughout western Europe the defeat still rankled. As early as 1396, in an effort to save the already doomed city, Charles’s great-great-great-grandfather John the Fearless had been captured when a Christian army estimated at a hundred thousand – the largest ever launched against the infidel – was smashed by Sultan Bayezit I at Nicopolis on the Danube. And in the much more recent past had not his rival Francis, while canvassing for the imperial election, declared that if he were successful, then within three years he would be either dead or in Constantinople? Sultan Suleiman was a formidable warrior indeed; but against the combined forces of the Christian West there was no reason to think that he was invincible.

The difficulty was, as Charles well knew, that comparative military strength was not really the point. In Spain, thanks to the long years of Muslim occupation, men could still talk seriously of launching a Crusade; in northern Europe they knew in their hearts that it was out of the question. Crusades belonged to the long-ago days of feudal Europe; now that the continent had become divided into individual nations and states – and in particular with the Reformation threatening to divide it even further – the sort of political unity necessary for such vast expeditions was no longer possible. For that very reason the question was never put to the test. Charles remained preoccupied with the affairs of Europe and the religious disputes by which, as a deeply pious Christian, he was obsessed. As a result, Emperor and Sultan were never to confront each other. Charles would never enter Constantinople; Suleiman would never occupy Vienna or Rome.

Was Charles interested in women? Not, certainly, as Francis was, or even Henry. (Suleiman, for obvious reasons, was in a class by himself.) He worked too hard, he travelled too much, and – while she lived – he loved his frail and beautiful Portuguese wife Isabella to distraction. Of his four illegitimate children, three were born well before his marriage; the fourth – who was to achieve fame as Don John of Austria, hero of the Battle of Lepanto – was born to a singer named Barbara Blomberg on his father’s own birthday, 24 February 1547, eight years after Isabella’s death.

Charles was the only one of our four princes to abdicate. He did so piecemeal: Naples and Sicily first, then the Netherlands, and finally Spain. Physically and mentally exhausted and tortured by gout, he withdrew to the monastery of Yuste in Extremadura, where, on 21 September 1558, he died of malaria.