Alan had to take refuge, along with his father Mathuedoi I, with King Æthelstan of England because the Norsemen had invaded Armorica.

Alan landed at Dol in 936, at the invitation of a monk, Jean de Landévennec, and with the aid of Æthelstan.

Alan II was closely allied with King Louis IV of West Francia, as both were exiles in England together at the court of Edward the Elder and Edward's son and successor Æthelstan.

Alan renounced the Cotentin, Avranchin and Mayenne and paid homage to Louis IV in 942.

Alan was buried in his capital, Nantes, in the church which he constructed to honor the Virgin Mary for his victory in liberating Nantes, initially known as la Chapelle de la Très Sainte Mère de Dieu,[a] now known as the Basilique Notre Dame in the parish of St Thérèse in Nantes.