Estrid Svendsdatter from Dansk Kvindebiografisk Leksikon 2003.

Estrid Svendsdatter born bef. 1010, died after 1057, was a Danish princess, daughter of Sweyn Forkbeard and Sigrid Storråde and sister of Cnut the Great. She was married to Ulf Jarl and the mother of Sweyn II Estridsen and Asbjørn Jarl. The dynasty that ruled Denmark in 1047-1412 was named after her. She was known in Denmark as dronning Estrid (queen Estrid), despite the fact that she was neither married to a king nor a queen regnant.
Estrid Svendsdatter from Dansk Kvindebiografisk Leksikon 2003:

Estrid was one of the great woman figures in the transitional period between the pagan Viking period and the Christian Middle Ages. Her mother was said to deny converting to Christianity, while Estrid when a widow saw to that the first stone church was built in Denmark. It was a chaotic period where the kings had enough to do just trying to keep the throne. The most obvious pretenders might suddenly have died or been killed - and this might give high ranked women like Estrid the chance to take power. Especially if they had a promising son - and she had. She also had the title of queen without having been married to a king. The best evidence of her royal importance at that time is the fact that her son Sven took name after her and called himself Estridsen. It was not in her cards that she had to live her life in Denmark. The first part of her life she was a more or less passive tool in an inconstant game about the power in northern Europe. The marriage plans for her meant probably that she alrady as a child had to take residence in her husband-to-be's homeland. She probably reached to stay in such various places like at the Russian rivers, in Normandy, England an finally at Zealand.

Estrid was a daughter of Sweyn Forkbeard who ab. year 1000 conquered Norway and a little later also made an attempt to subject England together with his son Cnut, the later famous king Cnut the Great. When his father died in 1014, Cnut, who was Estrid's half brother, became her guardian. She was very young, maybe only a child, but she was as a daughter of a king and a good card for the ambitious Cnut. Marriage agreements were one of the most important tools to create permanent alliances during the changeable power conditions. A single source claims that Estrid first was married to a young Russian prince, and if so most probably to one of Vladimir the Holy's four sons, who all fell in the civil war after Vladimir's death in 1015. But already ab. two years later Cnut the Great again used Estrid for new alliance purposes. He had succeeded in taking over the power in England, sealing it by marrying the widow Emma after his main opponent, the English king Aethelred. Queen Emma was a sister of duke Richard of Normandy, and Cnut now needed to strengthen the bands to his new brother-in-law. An agreement was made with Richard that Estrid had to marry his son Robert.

Something went wrong. Maybe Estrid was repudiated by Robert or the agreement fell to the ground for some reason before they got married. Robert died young, but he became the father of the later William the Conqueror, who in 1066 definitively brought England out of reach from the Nordic kings.

But one generation earlier Cnut was in solid power in England. And he now gave his half sister to one of his most trusted men, the English Jarl, Ulf. It looks like an attempt from Cnut to create a larger loyality around himself. But in the long run this alliance was a complete flop. Maybe Ulf was no longer loyal to Cnut - who else once after 1023 appointed him to govern in Denmark. Cnut must in any case have been affronted by the behaviour of his brother-in-law, for in 1026, when Ulf joined mass in Roskilde domkirke, he was killed by Cnut's men.

We know nothing of how Estrid took her fate. She lost the father of her sons by the mighty half brother's hand. It is even possible that the killing happened with her acceptance. Ulf's supposed conspiration against Cnut did not mean that Estrid disappeared in the dark. She got large estates in Skåne and Zealand as a compensation. And now being a rich widow she gave estate to Roskilde domkirke and built another church in Roskilde in remembrance of her husband. It was probably the first stone church in denmark. (gb: Estrid replaced the wooden church her father Sweyn Forkbeard had built beside the royal residence with a stone church). Her church-involvement also showed when she saw to that her promising son got a proper education, which at that time was equal to an international church education. This was positively noticed by pope Gregor 7 and others. Another son Asbjørn is not wellknown, other than he made an attempt in vain to conquer England in 1069. As a rich widow Estrid was in a place of her life and in a situation where it was possible for a woman to put power behind her will. She supported Sweyn in his long and difficult fight to gain supremacy over Denmark. This was her best opportunity in order to secure herself continuing influence. But her ambitions had often a hard time. For long periods Denmark was whole or partly under the Norwegian king Magnus' rule. When the place was getting too hot for her son, he went to live with his grandmother's Swedish family. The Swedish king Anund Jacob was Estrid's nephew, and Sweyn often took refuge at his cousin on several occassions.

Considering the circumstances of the Middle Ages Estrid reached a high age. She was born before 1010, and she died not until after 1057. This is known because her gift to Roskilde domkirke was sealed by Vilhelm who was a bishop in the years ab. 1057-73. Estrid was buried in Roskilde domkirke in one of the pillars of the choir. But the archaologists are not sure if it is her skeleton still being there.

John Carmi Parsson (red.): Medieval Queenship, 1993.

Optaget i Dansk kvindebiografisk leksikon 2003/translated January 2010 grethe bachmann

Addition from Magasinet Viking 2004: Two skeletons from burials in Roskilde Domkirke: Sven Estridsen and a woman's bones: It was believed that Sweyn Estridsen's mother was buried in the third of the pillars, the grave inscription said that it was "Margrethe also named Estrid", but a new DNA-test shows that she is not his mother. Much indicates that it is his daughter-in-law, who was buried opposite him. The skeleton is from a young woman. Museum's inspector from Roskilde Domkirkemuseum has published a book about Roskilde Domkirke's history, and her examinations indicate that it is Sweyn Estridsen's daughter-in-law in the grave. She was named Margrethe, and she was married to Sweyn's son Harald Hen. She gave the church some farms in Skåne, and the church showed its gratitude by through many years celebrating mass for her soul on her date of death 9. May. Therefore, says Annette Kruse, there is a good argument for believing that she had deserved to be buried in the church opposite her father-in-law Sweyn Estridsen. (Translated January 2010 from article in Magasinet Viking 2004) 
translation grethe bachmann ©​ copyright.