The gospel was first preached in Britain only a few years after the death of Christ. Gildas a Celtic priest and early church historian recorded that Britain received the gospel:
“... in the latter part of the reign of Emperor Tiberius.”
Tiberius reigned from 14 to 37 AD and is mentioned in the Gospel of Luke:
Now in the fifteenth year of the reign of Tiberius Caesar (29 AD), Pontius Pilate being governor of Judaea, and Herod being tetrarch of Galilee, … Annas and Caiaphas being the high priests, the word of God came unto John (the baptist) the son of Zacharias in the wilderness. (Luk 3:1-2)
A recent study has demonstrated that Christ's ministry only lasted just over one year this means He would have died in 30 AD. So using the timing mentioned by Gildas above the gospel was being preached in England within at least seven years of the death of Christ.
Tertullian wrote circa AD 190:
“…the Britons in parts inaccessible to the Romans Christ has truly subdued.”
Bede also recorded that missionaries were in Britain around AD 37. At least two of the twelve apostles actually visited our shores according to Eusebius (264 - 349):
“The apostles passed beyond the ocean to the Isles called the Britannic Isles.”
One of the apostles to visit Britain was Peter. Eusebius and Metaphrastes among several others recorded that Peter came to Britain during the expulsion of the Jews from Rome under Claudius. This expulsion is dated 54 AD and is mentioned in Acts 18:2. Note this is around 24 years after the death of Christ.
After these things Paul departed from Athens, and came to Corinth; And found a certain Jew named Aquila, born in Pontus, lately come from Italy, with his wife Priscilla; (because that Claudius had commanded all Jews to depart from Rome:) and came unto them. (Act 18:1-2)
Theodoretus the Bishop of Cyrrhus in 435 wrote:
“Paul liberated from his first captivity at Rome preached the Gospel to the Britons and to others in the west.”
Sophronius Bishop of Jerusalem in 600 wrote:
“Paul doctor of the Gentiles passed over the ocean to the island that makes a haven on the other side even to the land of the Britons even to Ultima Thrule.”
No one knows where Ultima Thrule is, Ireland? Arnoldus Mirmannus an early church historian wrote:
“Paul passed to Britain in the fourth year of Nero (AD 59) and there preached and afterward returned to Italy.”
When the Romans invaded Britain (43 AD) they eventually captured the famous Cambrian Celtic leader Caractacus (50 AD) and took him to Rome. He was allowed back to Britain to rule under the Romans while his family were held hostage in Rome. His father Bran was held in Rome from 51 to 58 when he returned home with the gospel. Caractacus’s son Linus and daughter Claudia continued in Rome as hostages. Claudia married a Roman Senator called Pudens. Paul wrote to Timothy:
Do thy diligence to come before winter. Eubulus greets thee, and Pudens, and Linus, and Claudia, and all the brethren. [2 Tim 4:21]
Not only were these famous British Celts mentioned in the Bible they also became martyrs.
Not only was the gospel preached it was received wholeheartedly by many. Eleutherius who was Bishop of Rome (c175 - 190) wrote to Lucius a tribal king in Britain recommending that both the Old and New Testament scriptures be referred to when creating laws. Bede recorded (303) that:
“The Britons preserved the faith which they had nationally received under King Lucius uncorrupted and entire and continued in peace and tranquillity until the time of Emperor Diocletian.”
He arrived in England in 597 sent by Pope Gregory to subdue the existing church and to subject it along with the nation to Roman Catholic Rule. Augustine knew he would find a strong indigenous church that claimed it was based on apostolic foundations. Knowing that ultimately he had the Emperor behind him He inspired the massacre in 604 of Cambrian (Welsh) clergy at Bangor in North Wales. Many were murdered for not "converting" to Catholicism throughout Britain.
It is said that under the influence of Augustine’s monks King Ethelbert stopped worshipping Thor and Woden and became a Christian. He gave Augustine his palace at Canterbury. The previously well established Celtic believers were not happy about this. In the main they refused to submit to him especially in Wales and Scotland.
A major win for Catholicism occurred in 663 when at the Synod of Whitby King Oswin of Northumbria decreed that the indigenous church was to follow the Roman and not the Celtic traditions.