Written by David Caldwell · 26 June 2025

Gildas and the Fall of Roman Britain: Voice of a Lost Age

Introduction

Gildas the Wise, a 6th-century Romano-British monk, remains one of the most important, if often misunderstood, figures in early British history. His only surviving work, De Excidio et Conquestu Britanniae (On the Ruin and Conquest of Britain), is one of the few textual witnesses to the twilight of Roman influence and the dawning of the Anglo-Saxon era in Britain. Written around AD 540, his text combines historical lament, religious exhortation, and political critique, offering both a window into the post-Roman world and a warning that resonates with later chroniclers such as Bede and Nennius.

Why Gildas Matters

Gildas is the first post-Roman British author whose work survives in full. He provides:

• Contemporary or near-contemporary testimony to events following the Roman withdrawal around AD 410.
• First-hand condemnation of native British rulers, naming five in particular: Constantine, Aurelius Caninus, Vortiporius, Cuneglasus, and Maglocunus (Maelgwn of Gwynedd).
• An account of the Saxon arrival, framed as both a military and moral catastrophe.
• A view shaped by Christian theology, interpreting Britain's suffering as divine punishment for moral decay.

Though Gildas does not name Arthur, his account of the battle of Mount Badon is seen by many later writers as referring to Arthur's legendary stand against the Saxons.

Gildas in Context

Gildas wrote during a turbulent era. The Roman legions had departed a century earlier, and Britain was fragmenting under pressure from internal division and external invasion. His writing blends religious fury with historical reflection, drawing heavily on Biblical allusion. To later readers, this makes his text a moral sermon as much as a historical source.

Contemporary and Later Chroniclers

• Bede (673–735): Writing nearly two centuries after Gildas, Bede's Ecclesiastical History of the English People relies in part on Gildas' work but frames the Saxon arrival in more providential terms. Bede views the English as instruments of divine correction who later embrace Christianity.
• Nennius (9th century): Author of Historia Brittonum, which draws upon Gildas and incorporates legendary material about King Arthur. Nennius expands Gildas' historical skeleton into a more mythic narrative.
• 
  

Timeline of Key Figures

• c. 410: Roman legions withdraw from Britain.
• c. 430s–450s: Traditional date for the Saxon mercenaries being invited into Britain.
• c. 495: Battle of Mount Badon (approximate date).
• c. 540: Gildas writes De Excidio et Conquestu Britanniae.
• 547: Death of Maelgwn of Gwynedd (Maglocunus), one of the kings Gildas condemns.
• c. 600s: Compilation of the Annales Cambriae, which reference Arthur and Badon.
• 673–735: Life of Bede; Historia Ecclesiastica written c. 731.
• c. 830s: Nennius writes Historia Brittonum.
• 
  

Conclusion

Gildas may not offer the detailed narrative of later historians, but his work is foundational for understanding the cultural and political fragmentation of Britain after Rome. He captures the voice of a man who watched a civilisation collapse, and sought to hold its remnants morally accountable. In doing so, he set the stage for the Christian chroniclers who followed and, indirectly, the legendary cycles of Arthur and the Britons.

Whether regarded as a prophet, polemicist, or proto-historian, Gildas remains essential reading for anyone seeking to understand how Roman Britain gave way to medieval England.

The Concise Gildas – Modern English in Bite-Sized Segments

Gildas – Preface (Modern English Summary)

1. I'm not writing this to boast or judge.
2. I don’t think I’m better than anyone else.
3. I’m just heartbroken about how far my country has fallen.
4. Goodness is being destroyed. Evil is spreading.
5. I want to mourn for Britain, and hope she recovers.
6. I’ve been silent for over ten years.
7. I didn’t feel worthy to speak out.
8. But I remembered how even saints were punished for small sins.
9. The Bible is full of warnings.
10. Even miracles didn’t save people from judgment.
11. I saw these things as a mirror of our own time.
12. The Church has fallen into ruin.
13. People once full of God’s word are now in filth.
14. I read the New Testament more clearly than before.
15. Jesus warned that the unfaithful will be cast out.
16. Some will be welcomed; others rejected.
17. Some will knock, but the door will stay closed.
18. I believe in God's mercy, but I also fear His justice.
19. Even Peter was tested. Judas fell.
20. Early Christians shared everything, but some lied and were punished.
21. Our own time is full of pride and complacency.
22. I kept thinking, “Who am I to speak?”
23. Britain has leaders, bishops, and priests.
24. But they are overwhelmed.
25. Eventually, I felt I had to speak.
26. If God once used a donkey to deliver truth, maybe He can use me.
27. So I’m writing plainly, out of love for Christ’s people.
28. The faithful will read with tears. The corrupt will squirm.

Gildas – Section 2 (Overview of Topics)

1. I will now tell the story of Britain.
2. Her geography, her rebellions, her defeats.
3. Her religion, her martyrs, her heresies.
4. Her tyrants and invaders.
5. Her first devastation, and her defences.
6. Her second devastation, and revenge.
7. Her third devastation, and famine.
8. Her appeals for help to Rome.
9. Her short victory, and her renewed sins.
10. The shock of new enemies.
11. The great plague.
12. Her councils and decisions.
13. Her final, most terrible enemy.
14. The destruction of her cities.
15. The survival of a small remnant.
16. And at last, the peace God granted in my own time.

Gildas – Section 3 (Britain: A Land Once Blessed)

1. Britain lies on the edge of the known world.
2. It’s an island in the ocean, lying to the west.
3. It’s fertile, rich in resources, and pleasant to live in.
4. It once had 28 cities, many castles, and well-built homes.
5. The land was filled with rivers, forests, and wildlife.
6. In earlier times, it followed Roman customs.
7. Roman troops and laws protected the people.
8. Christianity arrived while the Romans were still here.
9. Some Christians were martyred under Roman emperors.
10. Persecution gave way to peace when Rome embraced the faith.
11. Churches were rebuilt, and true religion flourished.
12. But peace led to pride.
13. Pride led to laziness and sin.
14. People turned away from God.
15. Leaders became cruel and corrupt.
16. The church was filled with jealousy and division.
17. God, seeing this, allowed enemies to strike.
18. Punishment came from beyond the sea.

Gildas – Section 4 (Invasion and Betrayal)

1. First came the Picts and Scots.
2. They attacked from the north and west.
3. The British people were terrified.
4. They cried out to Rome for help.
5. Roman troops came and drove the invaders out.
6. The British built a wall across the island.
7. But after Rome left, the enemies came back.
8. With no army to protect them, the Britons panicked.
9. Their leaders made a disastrous decision.
10. They invited Saxons from across the sea to help.
11. The Saxons arrived as allies, but stayed as conquerors.
12. At first, they fought off the Picts and Scots.
13. But then they demanded more food, land, and rewards.
14. When refused, they turned on the Britons.
15. Towns were burned. People were slaughtered.
16. Survivors fled to mountains, forests, and caves.
17. Fire and sword swept the land.
18. Britain was laid waste by those she had invited in.

Gildas – Section 5 (The Groans of the Britons)

1. The Britons sent letters to Rome again.
2. They begged the Roman general Aetius for help.
3. Their message said, “The barbarians push us back. The sea drives us out. Between both, we are killed.”
4. But Rome could no longer save them.
5. No army came. No reinforcements arrived.
6. Left to themselves, the Britons tried to fight.
7. Sometimes they won small victories.
8. But soon they returned to their sinful ways.
9. Pride returned. Justice vanished.
10. God’s anger burned hotter.
11. Another punishment was coming.
12. This time, even worse than before.

Gildas – Section 6 (Ambrosius and Mount Badon)

1. Then came a glimmer of hope.
2. A man named Ambrosius Aurelianus rose up.
3. He was of Roman descent and had survived the earlier troubles.
4. He gathered the remaining Britons.
5. Under his leadership, they began to resist.
6. Battles went back and forth.
7. Sometimes the Saxons won; sometimes the Britons.
8. Then came a great victory at Mount Badon.
9. Many Saxons were killed.
10. This gave the Britons a moment of peace.
11. But it didn’t last.
12. With peace came complacency.
13. The people forgot God once again.
14. They sank back into sin.
15. And new disasters were waiting.

Gildas – Section 7 (The Return to Sin)

1. After Mount Badon, the British had peace.
2. But they grew lazy and arrogant.
3. Their sins increased.
4. The kings became worse.
5. They were proud, greedy, and cruel.
6. Each tried to outdo the others in wickedness.
7. They ignored God’s law.
8. They oppressed the poor.
9. They committed adultery and murder.
10. Even church leaders joined in their corruption.
11. Some priests were good, but many were not.
12. Gildas names and rebukes five kings for their sins.
13. He warns them that God’s judgment is near.
14. He calls them to repent before it’s too late.

Gildas – Section 8 (Five Sinful Kings)

1. Gildas rebukes five British kings by name.
2. First is Constantine: corrupt, violent, and impure.
3. Then Aurelius Caninus: proud and oppressive.
4. Next is Vortiporius: a tyrant hated by his people.
5. Then Cuneglasus: a warlord who mocks religion.
6. Last is Maglocunus (Maelgwn): once good, now worst of all.
7. Gildas accuses them of adultery, betrayal, and bloodshed.
8. He urges them to repent while they still can.
9. Otherwise, they will face divine punishment.
10. Their thrones are shaky. Their legacy is shame.

Gildas – Section 9 (Corruption in the Church)

1. Gildas now turns his criticism to the Church.
2. Many priests and clergy have become corrupt.
3. They love money more than holiness.
4. They seek honour instead of humility.
5. They ignore God’s teachings.
6. Some take bribes and twist justice.
7. They dress richly but live sinfully.
8. Their words sound holy, but their hearts are not.
9. Gildas mourns the loss of true shepherds.
10. He calls for a return to purity and discipline.
11. He urges church leaders to repent.
12. Only then can the Church be healed.
13. True pastors must teach with humility and courage.
14. They must be examples of godliness to their people.
15. Gildas prays for reform, for a Church worthy of Christ.

Gildas – Section 10 (Closing Warnings and Reflection)

1. Gildas compares corrupt church leaders to wolves in sheep’s clothing.
2. He says they love their own bellies more than God’s flock.
3. They chase after worldly things, riches, honour, and comfort.
4. They don’t teach, or if they do, their words are empty.
5. They no longer act as watchmen or shepherds.
6. The people are spiritually starving, led by blind guides.
7. Gildas says such leaders will face harsh judgment.
8. He urges them to repent before it’s too late.
9. He warns that the fire of divine anger is near.
10. Christ will come not in humility but in power.
11. Each person will be judged according to their deeds.
12. The corrupt will be cast away. Only the faithful will rejoice.
13. Gildas ends with a plea: return to righteousness.
14. His final message is a call to repentance, reform, and fear of God.

Legacy and Legends

Gildas' legacy goes beyond his text. Later myths, explored in 19th-century newspaper cuttings, link him to miraculous visions, prophecies, and even connections with Glastonbury Abbey. Though little is known about his life, some traditions claim he was the son of Caw, a northern ruler, and that he travelled widely, preaching and founding monasteries in places such as Brittany and Wales.

He is said to have lived on an island in the Bristol Channel, possibly Steep Holm or Flat Holm, seeking solitude from worldly corruption. Later traditions suggest he crossed to Brittany, where he founded a monastery at Rhuys and helped spread Christianity.

Medieval writers often elevated him to sainthood. In some legends, he contended with King Arthur; in others, he fled into solitude after confronting moral decay. These stories, though historically uncertain, reflect how his warnings echoed for generations.

Ultimately, Gildas’ true importance lies not in myth, but in his unwavering call to truth. He reminds us that history is not only what happens, but how we choose to remember and respond.