Complex sentence: Following the death of King Henry in late 1272, with the new King Edward I of England away from the kingdom, the rule fell on three men, one of whom, Roger Mortimer was one of Llywelyn's rivals in the marches.
Split into simpler sentences: Following the death of King Henry in late 1272, with the new King Edward I of England away from the kingdom, the rule fell to three men. One of whom, Roger Mortimer was one of Llywelyn's rivals in the marches.