The historian Walter Goffart argues that Bede based the structure of the "Historia" on three works, using them as the framework around which the three main sections of the work were structured. For the early part of the work, up until the Gregorian mission, Goffart feels that Bede used "De excidio". The second section, detailing the Gregorian mission of Augustine of Canterbury was framed on "Life of Gregory the Great" written at Whitby. The last section, detailing events after the Gregorian mission, Goffart feels were modelled on "Life of Wilfrid". Most of Bede's informants for information after Augustine's mission came from the eastern part of Britain, leaving significant gaps in the knowledge of the western areas, which were those areas likely to have a native Briton presence.