 Half a century later, however, Somerled, the husband of Godred Crovan's granddaughter, led a successful revolt against Norway, transforming Suðreyjar into an independent kingdom.Somerled built the sea fortress of Claig Castle on an island at the southern tip of Jura, establishing control of the Sound of Islay; on account of the Corryvreckan whirlpool, this essentially gave him control of the sea traffic between the Scottish mainland and the Hebrides.After his death, nominal Norwegian authority was re-established, but de facto authority was split between Somerled's sons and the Crovan dynasty.