Career
He holds a Master"s degree in Microeconomics from the University of Copenhagen and used to teach economics at Menntaskólinn í Kópavogi. Willum began his career at KR before moving on to Breiðablik and later Þróttur where he started his manager career. He represented Iceland at youth level both in basketball and football.
Willum led Þróttur to Iceland"s top league, the Úrvalsdeild in 1997.
The wait had been long as Þróttur last played at the top level in 1985. In 2000 he became the manager of Haukar, and in 2002, he was appointed manager of KR and led them to two successive championships in 2002 and 2003.
In 2004 KR finished without a title and Þórsson"s contract was not renewed. He took charge of Valur who had just been promoted to the Úrvalsdeild and finished the 2005 season in 2nd place after champions Fachhochschule . He left with mutual agreement on 1 July 2009.
On 29 September 2009, after the season had finished for the year, he was appointed the new manager of Keflavík.
In November 2010, Willum was appointed as the first manager for the Icelandic futsal team Willum has taken active part in politics with the Progressive Party. In the 2013 Icelandic parliamentary election he was elected to the Alþingi.