The 4th century was a time of great change for Christianity. After centuries of squabbling over the canonicity of the Bible, leaders of the Christian Church from all over the the Middle East, Africa and Europe met at the Council of Nicaea to finally settle how the text of the Bible should read. The Fifth Doctor, Peri and Erimem were on hand at the conference, held in 325. (AUDIO: The Council of Nicaea) Also, the Second Doctor likely befriended Saint Nicholas in the early part of the century, (PROSE: Saint Nicholas's Bones) and the Eighth Doctor and Charley stopped a Nimon invasion of Roman Britain. (AUDIO: Seasons of Fear)

As with most centuries of the first two millennia, the 4th century was home to Jack Harkness, Amy Pond and an Auton duplicate of Rory Williams. A version of Jack from around the time of the deaths of Toshiko Sato and Owen Harper existed in this century, having been buried alive in the 1st century by his brother, Gray. He perpetually died and resurrected an unknown number of times in an earthen tomb underneath Cardiff. (TV: Exit Wounds) Meanwhile, a near-dead Amy Pond was kept alive inside the Pandorica, beginning in the 2nd century. An Auton version of Rory kept vigil near her the entire time. They both awaited a moment in the mid-1990s when a young Amelia Pond would touch the outside of the Pandorica and restore Amy to full health. (TV: The Big Bang)

It was substantially unclear whether the events of the subsequent Big Bang Two erased Amy and Rory's presence in the 4th century. This ambiguity was caused, in part, because the non-Auton, married Rory Williams claimed to have remembered being "made of plastic" at his wedding reception, suggesting that, at least inasmuch as he was concerned, he and Amy were present in the 4th century. (TV: The Big Bang) Amy seemed to also remember those events, and displayed a fondness for the Auton Rory both during her honeymoon (TV: A Christmas Carol) and during a kind of lullaby to her newborn child Melody Pond. (TV: A Good Man Goes to War)