Though William was her successor, his rule was nominal, all the more so because he was still too young to rule in his own right and was put under the regency of his mother's sister Agnes and her husband, Marianus II of Logudoro.
Meskipun William adalah pewarisnya, pemerintahannya nominal, semuanya lebih karena dia terlalu muda untuk memerintah dengan haknya sendiri dan ditempatkan di bawah Kabupaten Agnes saudara perempuan ibunya dan suaminya, Marianus II dari Logudoro.