Chelles had been the site of a Merovingian palace, the villa Calae. A church, dedicated to Saint George had been founded at Chelles by Queen Clothilde. King Chilperic I and his wife Fredegund frequently resided there, and Chilperic was assassinated near Chelles in 584. Balthild named Bertilla as the first abbess of the monastery. Balthild herself retired to Chelles in 664 and died there in 680, where she was also buried. Her possessions were treated as relics at Chelles. Other royal and noble nuns and abbesses included Mildrith may have been educated at Chelles.