The Swedish royal castle on the Nyköpingsån where King Birger seized his two brothers at a Christmas feast in 1317 and left them to die in the cellar — the act that destroyed his own reign.
Nyköping Castle in Södermanland was the site of the Nyköping Banquet in December 1317, when King Birger of Sweden imprisoned his brothers Valdemar and Erik at a Christmas feast. Their subsequent confinement and death became one of the most infamous episodes of treachery in Swedish royal history.
The castle began as a defensive tower at the river mouth in the late twelfth or early thirteenth century, guarding the approach from the Baltic to Södermanland, and grew into one of the principal royal castles of the kingdom in the Bjälbo century.
Magnus III of Sweden left three sons: Birger, who was crowned king, and the dukes Erik and Valdemar, who held great territorial lordships and behaved as rulers in their own right. The quarrel between them ran for twenty years and used this castle repeatedly.
In 1306, at the Håtuna games, the dukes seized the king at a royal estate in Uppland and carried him off as a prisoner to Nyköping. He was released in 1308, and by the settlement made at Helsingborg in 1310 the kingdom was carved into three lordships — a partition that satisfied nobody and left the king the weakest of the three.
On 11 December 1317 Birger invited his brothers to keep Christmas with him at Nyköping. They came with a small following, as guests, and were seized in the night and thrown into the cellar of the castle tower.
The trap worked in the narrow sense that the dukes never came out. They died there in 1318 — starved, by the tradition that gave the episode its lasting horror, though the manner of their deaths is not documented. The invitation and the arrest, however, are: the king had used the obligation of hospitality as a weapon, and in a political culture built on guest-right that was the unforgivable part.
The Nyköping Banquet destroyed Birger’s political position. His brothers’ deaths provoked a Swedish noble uprising that deposed him and led to the accession of Magnus Eriksson in 1319. The castle’s name became synonymous with royal betrayal in Swedish historical memory.
Birger fled to Denmark and died there in 1321. His son and heir Magnus Birgersson was captured and executed at Stockholm in 1320, so the line was ended as well as the reign. The three-year-old elected in his place was Duke Erik’s son, who was also king of Norway: the murders at Nyköping put a Norwegian-Swedish union on the throne.
An earlier royal prisoner had already died within these walls: Valdemar of Sweden, deposed by his brother Magnus in 1275, ended his life in confinement at Nyköping in 1302, which makes the castle the scene of two separate dynastic eliminations a generation apart.
At the end of the sixteenth century Duke Charles, later Charles IX, rebuilt the medieval fortress as a Renaissance palace. It burned with the town in 1665 and was not restored; some of its brick went into the building of the royal palace at Stockholm. The King’s Tower and the gatehouse survive, and hold the Sörmland museum.