Board Thread:Questions and Answers/@comment-184.88.25.24-20131112235645/@comment-5102537-20160916144745

Morgause was not smuggled out of Camelot as a baby during the Great Purge. She was several years older than Morgana (otherwise they wouldn't have chosen an actress who is 10 years older than Katie McGrath).

Uther told Morgana in season one that she wasn't even "around"  when the Great Purge took place (probably meaning not in Camelot but with her parents somewhere else). The Great Purge started directly after Arthur's birth  (as was confirmed by Uther in the very first episode of season one when they celebrated the capture of the Great Dragon "20 years ago") which means that Morgause was anything but a baby at that point of time.

Obviously, the Great Purge lasted - to all our astonishment, I have to say - only one year (Uther stated that 20 years ago the Great Dragon was captured and the land "freed from the evil sorcery". Shortly after that, Arthur came of age which most likely means 21 years). Since Morgana was 10 years old when she lost her father, it didn't happen during the Great Purge. She might have been a little child when the purge started but she surely wasn't 10 years older than Arthur. Moreover, she accused Uther of having lost her father because Uther allegedly sent him into battle and failed to send reinforcements. There was no mentioning of the Great Purge whatsoever.