Svein almost certainly died of natural causes, possibly after a fall from a horse, but no reliable source tells us for sure. However, by the end of the eleventh century legends had developed about Svein's crucially-timed death, claiming that it had a supernatural cause. The Canterbury monk Osbern, writing in the 1080s, says only that Svein was 'killed in a terrible manner by Almighty God' (sadly, even Osbern's love of colourful detail does not extend to telling us what this terrible manner was), but in c.1095 a monk of Bury St Edmunds gives the answer, subsequently repeated by many later chroniclers: it was St Edmund of East Anglia who struck Svein down.
This is how John of Worcester describes his death:
After many cruel atrocities, which he perpetrated both in England and in other lands, the tyrant Swein filled up the measure of his damnation by daring to demand enormous tribute from the town where the incorrupt body of the precious martyr Edmund lay, a thing no one had dared to do before... He very frequently threatened that if it were not speedily paid he would destroy utterly the martyr's church, and he would torture the clergy in various ways. In addition, he frequently disparaged the martyr himself in many ways - he dared to say that he had no sanctity - and, because there were no bounds to his malice, divine vengeance did not allow the blasphemer to live any longer.
At last, when the evening was approaching of the day on which, at the general assembly which he held at Gainsborough, he repeated the same threats, at a time when he was surrounded by Danish troops crowded together, he alone saw St Edmund, armed, coming towards him. When he had seen him, he was terrified and began to shout very noisily, saying "Help, fellow-warriors, help! St Edmund is coming to kill me!" And while he was saying this he was run through fiercely by the saint with a spear, and fell from the stallion on which he sat, and, tormented with great pain until twilight, he ended his life with a wretched death on 3 February.
The Chronicle of John of Worcester, trans. Jennifer Bray and P. McGurk (Oxford, 1995) vol. ii, p. 477.
A 13th-century depiction of Svein's death (CUL MS. Ee.3.59, f.4v)
The point of this story is that St Edmund himself, king of East Anglia in the ninth century, had been killed by Danish invaders, so this is a kind of long-delayed revenge. Edmund, after death, was doing what the living English king had signally failed to do, and mounting an effective response to the Danes. The story is probably based on a legend about the death of Julian the Apostate, who was killed in similar fashion by St Mercurius; it thus introduces an element of religious hostility into Anglo-Danish conflict which was in fact absent from any of Svein's own attacks, and had not been an important factor in Viking raiding for years (if it ever really was). Svein had a reputation in England as a notorious pagan, but this was probably undeserved; there's no reason to think that his raiding was the result of religious or ethnic hostility, whatever later English sources might have claimed.
We don't have any evidence for this story before the end of the eleventh century, so I'm inclined to say it's less about Svein than it is about the second, more traumatic conquest of that century: in the aftermath of the Norman Conquest there was obvious appeal in a story about dead saints taking on England's conquerors. It's not the only such legend from that period: St Etheldreda of Ely, not to be outdone, had apparently taken to stabbing Norman sheriffs with her staff, and the corpse of St Edith of Wilton supposedly terrorised Cnut (in a tale which is very unlikely to be earlier than the twelfth century). So the story of Svein and St Edmund may not be about Svein in particular so much as about a general sense of helplessness and injustice in certain English abbeys in the late eleventh/early twelfth century.
Whatever the origins of this specific story, it's true that Svein had a bad reputation in England even in his lifetime: twenty years of raiding a country will do that! William of Malmesbury's version of the story of Svein's death goes on to claim that Cnut learned a lesson from it, and paid due honour to St Edmund when he later became king: he founded a monastery at Bury St Edmunds (this is true) and built a trench around the town to keep tax-collectors out (I don't know if this is true, but it sounds useful). He says:
Tax collectors, who run riot elsewhere, regarding right and wrong as the same thing, there turn suppliant and stop their lawsuits on this side of St Edmund’s trench, having seen the penalty paid by their many brethren who decided to continue past it. This trench was made on the orders of king Cnut, who was warned to do this good thing by the unhappy end of his father Swegn. For in the time of king Æthelred, Swegn was laying waste the whole of England and breathing out no less terrifying threats in the district of St Edmund, when, so the story goes, he was given a gentle admonishment by the martyr in a dream. Swegn with barbarian ineptitude replied with some roughness, so the saint struck him with a pole and killed him. Because he had been struck in his sleep, a long delay intervened before the author and manner of his death was revealed to those standing outside. The guardians of the body to their amazement had indeed heard a conversation between people arguing and the sound of a blow. King Cnut knew of this incident, so did all he could to mollify the saint.
William of Malmesbury, Gesta Pontificum Anglorum, ed. and trans. Michael Winterbottom and R. M. Thomson (Oxford, 2007), vol. ii, p. 101.
This is William's own take on the situation a century after Cnut's death, but he's basically right in his description of the dynamic: whether or not people were already saying in the 1020s that Edmund had slain Svein, Cnut generally did his best to make himself look as different from his father as possible. It probably suited him pretty well that Svein had a reputation as a savage pagan Dane, because what makes a king look better than comparison with a savage pagan predecessor? By contrast to Svein, Cnut looked pious, generous, reasonable, and law-abiding, even when he wasn't being any of those things. But this is probably one of the occasions where Cnut was saying very different things to different audiences: the English church would have lapped up any repudiation of Svein, any rhetoric about 'learning from the errors of my fathers', but in the Encomium Emmae Reginae (written after Cnut's death for his wife), which reflects a more pro-Danish point of view, Svein is highly praised:
Svein, king of the Danes, was, I declare, as I have ascertained from truthful report, practically the most fortunate of all the kings of his time, so that, as seldom occurs, his happy beginning was followed by an end much happier from both the spiritual and the worldly point of view. He, then, derived his descent from a most noble source, a thing of foremost importance among men, and the government of the empire which he administered brought him great worldly honour. The divine power granted him such great favour, that even as a boy he was held by all in close affection, and was hated only by his own father. No fault of the boy deserved this: it was due only to envy. When he grew to be a young man, he increased daily in the love of his people, and, accordingly, his father's envy increased more and more, so that he wished, not in secret, but openly, to cast him out, affirming by oath that he should not rule after him. The army, grieved by this, deserted the father, adhered to the son, and afforded him active protection...
He could have found no activity so irksome, that his soldiers would have been unwilling, if he impelled them to it, for he had rendered them submissive and faithful to himself by manifold and generous munificence. So that you may realise how highly he was regarded by his men, I can strongly affirm that not one of them would have recoiled from danger owing to fear of death, but, unafraid, would have gone out of loyalty to him against innumerable enemies alone, and even with bare hands against armed men, if only the royal signal should be given to them as they went.
And this is what he says about Svein's death:
When the king who has been often referred to was enthroned over the whole country of the English, and when already scarcely anyone resisted him, he survived for a period which was short, although it was glorious. Feeling, therefore, that the dissolution of his body was threatening him, he summoned his son Knutr, whom he had with him, and said that he must enter upon the way of all flesh. He exhorted him much concerning the government of the kingdom and the zealous practice of Christianity, and, thanks be to God, committed the royal sceptre to him, the most worthy of men.
Encomium Emmae Reginae, trans. Alistair Campbell (London, 1949), pp. 9-11, 15.
'The zealous practice of Christianity'? Well, there you go. Believe whichever version you choose; they're all fiction...
The monks of Bury St Edmunds, who had perhaps invented the story of St Edmund's killing of Svein in the first place, took it and ran with it, and by the fifteenth century we can find it depicted in illustrations of John Lydgate's Life of Edmund (above and below).
Edmund is in contemporary armour and Svein is dressed in the clothes which, to a fifteenth-century eye, said 'pagan' - whether the pagan in question was supposed to be a Viking or a Saracen!
Svein invading England (via wikipedia)
But all of this is unfair to Svein, who deserves better, on the 1000th anniversary of his death, than to be remembered as the victim of supernatural tit-for-tat. Svein has perhaps suffered more than anyone from the trend I discussed in my first post on the Danish Conquest, an unwillingness to take the Vikings seriously and an inclination to believe just about anything later historians said about them. Svein's reputation as a bloodthirsty pagan really is unwarranted, and he certainly doesn't deserve to be compared to Hitler (!), as in a recent BBC article about him:
For 20 years, Sweyn, a "murderous character" who deposed his father Harold Bluetooth, waged war on England.
And exactly 1,000 years ago, with his son Canute by his side, a large-scale invasion finally proved decisive.
It was a brutal time, which saw women burned alive, children impaled on lances and men dying suspended from their private parts.
Gainsborough historian Darron Childs says: "It is perhaps one of the reasons why Sweyn has been largely forgotten.
"It's hard to make a big thing of someone so bad - it would be a bit like celebrating Hitler. It's a difficult thing to try and overcome."
Did the Vikings impale children on lances? No, of course they didn't. Much later Icelandic saga-writers and English historians sometimes said they did, because even in the Middle Ages people liked to exaggerate the excesses of Viking violence, but we shouldn't go around repeating this as sober historical fact. 'Impaling children on lances' was a cliche beloved by twelfth-century historians, and it's not to be taken literally - it's an obvious reference to the Massacre of the Innocents, intended to suggest a general idea of 'barbarian' (that is, non-Norman) violence, and it's applied to the Scots as well as the Danes. And I'll say again that there's no reason to think Svein's attacks on England had an ideological or religious motivation. Svein was an effective military leader, who took the strategies of raiding and alliance-forming which had served Vikings well for centuries and developed them into a form of empire-building; we can have opinions on the morality of that, but they will almost certainly be anachronistic and unhelpful in trying to understand the events of the eleventh century.
So I think it's possible to admire Svein without 'taking sides' or pronouncing on the justice of his invasion of England. (The desire to take sides in a historical dispute is always a mystery to me; I find Anglo-Saxons and Vikings equally fascinating and you'll never make me choose between them!) The popular myth of Viking raids is that they are haphazard, bloodthirsty, irrational, seeking nothing but mindless destruction; but in tracking the unfolding events of 1013, I was struck once more by the care with which Svein's final invasion was planned and executed, and the skill with which he exploited the key faultlines in contemporary English politics. I wrote about it at greater length here. There's a remarkable contrast between this and the chaotic, faction-driven decision-making headed by Æthelred, a king who was 'imbellis quia imbecillis' (in Osbern's snappy phrase). Because of the way the sources survive, we only really get to hear from Svein's enemies, but it would be fascinating to know what his supporters might have said about him; the Encomium, for all its flaws as a historical document, comes the closest to giving them a voice, and it lays heavy emphasis on his men's loyalty to him. Svein never got a chance to show what he could do as king of England - but what might have happened if he had lived a little longer?