Page "Alan III, Duke of Brittany" Paragraph 5

In 1037 at the death of Robert, Archbishop of Rouen, the protection of young William was now left to Alan III and his cousin Gilbert who tentatively held Normandy together.

They appointed Mauger to the now vacant see of Rouen and his brother William as count of Arques, attempting to gain their support for Duke William.

On 1 October 1040, while besieging a rebel castle near Vimoutiers in Normandy, Alan III suddenly died.

According to Orderic, he was poisoned by unnamed Normans.