 Crawford (1987) suggests that influence from the south rather than the north was "usually predominant" whilst admitting that the islands probably formed "groups of more or less independent communities".Godred Crovan became the ruler of Dublin and Mann from 1079 and from the early years of the 12th century the Crovan dynasty asserted themselves and ruled as "Kings of Mann and the Isles" for the next half century.The kingdom was than sundered due to the actions of Somerled whose sons inherited the southern Hebrides whilst the Manx rulers held on to the "north isles" for another century.