Complex sentence: Dunstan, whilst in exile became influenced by the Benedictines of Flanders and a pro-Dunstan, pro-Benedictine party began to form around Athelstan Half-King's domain of East Anglia supporting Eadwig's younger brother Edgar.
Split into simpler sentences: Dunstan, whilst in exile, became influenced by the Benedictines of Flanders. A pro-Dunstan, pro-Benedictine party began to form around Athelstan Half-King's domain of East Anglia and supporting Eadwig's younger brother Edgar.