Early evangelisation in Scandinavia was begun by Ansgar, Archbishop of Bremen, "Apostle of the North". Ansgar, a native of Amiens, was sent with a group of monks to Jutland in around 820 at the time of the pro-Christian King Harald Klak. The mission was only partially successful, and Ansgar returned two years later to Germany, after Harald had been driven out of his kingdom. In 829, Ansgar went to Birka on Lake Mälaren, Sweden, with his aide friar Witmar, and a small congregation was formed in 831 which included the king's steward Hergeir. Conversion was slow, however, and most Scandinavian lands were only completely Christianised at the time of rulers such as Saint Canute IV of Denmark and Olaf I of Norway in the years following AD 1000.