Answer:
The Celts fled to Ireland with the invasion of the Anglo-Saxons
Step-by-step explanation:
The Anglo-Saxons were a Germanic tribe with a diverse background mostly associated with modern-day Germany and Denmark.
With the gradual decline of the Roman Empire, the province of Britannia, like rest of Europe was vulnerable to local warlords.
Gradually, the Anglo-Saxons found their new autonomy from the Romans, empowering, and gradually decided to expand and build a small Empire.
Locally, they were in direct confrontation wit the Celtic people, who had to flee to the Isle of Ireland.