The Lions looked dead and buried as they trailed 2-0 at the break but it could have been a lot worse but for goalkeeper David Forde's penalty save early in the game. However the Millwall manager decided to change things at the interval, making two substitutions and it paid off as Harris rolled back the years and scored his first hattrick in eight seasons.
"It was a tremendous comeback and an outstanding hattrick," said a delighted Jackett after the game. "A first-class hattrick in the way he took his goals.
"It was a great win for us at the end of a real tough run. We've had 11 games in five weeks, it was a close game in the end but our character and our fitness just edged it."