Mills crossed for a crucial second half score as England sought to make the game safe and then floated a lovely cut out pass to put winger Christian Wade in for a score.
Speaking after the game, the 19 year old centre admitted that the win was welcome but that there is still plenty to work on.
"We're really happy about getting the win, but there's no way we've peaked yet. There's a lot to work on after the Scotland game, but to score five tries when you're not at your best is always a good sign."
"It was hot out there which maybe limited us in terms of the amount of our running, but we still showed glimpses of what we're capable of."
"Scotland made things tough for us and their set piece was pretty good - as we knew it would be, and they got behind us a few times, and that's something we'll take a look at."
Two wins from their opening two pool games see England sitting in second place in their table as South Africa, the Baby Boks, have also won two from two. It's all to play for in the final group game.
"South Africa are next and we know what kind of a side they are. They're good with the ball in hand so we'll be looking to keep as much possession as possible."
"It's a winnable game and if we want to win the whole thing then we'll need to play and beat these southern hemisphere sides."