him with his young son by Queen Emma, Harthacnut, whom he had designated the heir of his kingdom. The banishment of Thorkell the Tall in 1021 may be seen in relation to the attack on the Wends. With the death of Olof Skötkonung in 1022, and the succession to the Swedish throne of his son Anund Jacob bringing Sweden into alliance with Norway, there was cause for a demonstration of Danish strength in the Baltic. Jomsborg, the legendary stronghold of the Jomsvikings (thought to be on an island off the coast of Pomerania), was probably the target of Cnut's expedition. Successful, after this clear display of Cnut's intentions to dominate Scandinavian affairs, it seems that Thorkell reconciled with Cnut in 1023. When, in spite of this, the Norwegian king Olaf Haraldsson and Anund Jakob took advantage of Cnut's commitment to England and began to launch attacks against Denmark, Ulf gave the Danish freemen cause to accept Harthacnut, still a child, as king. This was a ruse on Ulf's part since his role as caretaker of Harthacnut gave him the reign of the kingdom. Upon news of these events, Cnut set sail for Denmark to restore himself and to deal with Ulf, who then got back in line. In a battle known as the Battle of the Helgeå, Cnut and his men fought the Norwegians and Swedes at the mouth of the river Helgeå, probably in 1026, and the apparent victory left Cnut as the dominant leader in Scandinavia. Ulf the usurper's realignment and participation in the battle did not, in the end, earn him Cnut's forgiveness. Some sources state that the brothers-in-law were playing chess at a banquet in Roskilde when an argument arose between them, and the next day, Christmas 1026, one of Cnut's housecarls killed the jarl with his blessing, in Trinity Church, the predecessor to Roskilde Cathedral. Journey to Rome His enemies in Scandinavia subdued, and apparently at his leisure, Cnut was able to accept an invitation to witness the accession in Rome of the Holy Roman Emperor Conrad II. He left his affairs in the north and went from Denmark to the coronation at Easter 1027, which would have been of considerable prestige for rulers of Europe in the Middle Ages. On the return journey he wrote his letter of 1027, like his letter of 1019, informing his subjects in England of his intentions from abroad