The Right Reverend Knut Ansgar Nelson was born in Fredeoriskvaek, Denmark on October 1, 1906. He came to the United States in 1925 to study art and took work in Salem, Massachusetts where he converted to Catholicism. Shortly thereafter he entered Portsmouth Priory and was clothed as a novice at Fort Augustus Abbey. He took his solemn vows there in 1935 and studied philosophy at Maria Laach in Germany.
Having returned to Portsmouth, Dom Ansgar was ordained to the priesthood on May 22, 1937. He taught classics in the school at Portsmouth and was Junior Master and Master of Studies in the Monastery. He earned a Master of Arts degree in the classics from Brown University in Providence.
At Brown he met Rabbi William Braude with whom he began to study Hebrew. During the war Dom Ansgar was chaplain to the German prisoners in Newport.
On September 8, 1947 he was consecrated Bishop and co-adjutor of the Vicar Apostolic of Sweden, Bishop John Mueller. In 1957 Bishop Ansgar succeeded Bishop Mueller, becoming the second bishop of Stockholm. In 1962 Dom Ansgar was forced to resign his seat because of poor health. He was chaplain to nuns in Switzerland until he returned to Portsmouth in 1967.
Bishop Ansgar took up again his old interest and taught Philosophy and Theology to monks and students in the school. He resumed his study of Hebrew with Rabbi Braude, and rapidly settled into community life.
In the last decade he suffered from a variety of complaints and illnesses. In March he was admitted to the hospital in Newport and a week later on March 31 he died there.