Agents
Augustine of Canterbury
See also references for related subjects.
Flechner, Roy, “Dagán, Columbanus, and the Gregorian mission”, Peritia 19 (2005): 65–90. 
abstract:
An attempt to sketch the biography of Dagán, the Irish bishop who met the Gregorian missionaries in Kent, and to establish whether the Irish church concerned itself with the mission. Several categories of sources are considered: contemporary epistles (by Gregory, Columbanus, Lawrence), annals, canon law (Hibernensis, Synodus Patricii) liturgical material (Stowe Missal, martyrologies), hagiography (saints’ Lives and genealogies), saga (Bórama), and Bede’s HE.