Not championship, but the league 2 playoffs, Mansfield beat Northampton 1-0 [3-1 on agg] to reach the league 2 playoff final.
Remember Northampton from the last match of the season, won 3-1 but because Bristol Rovers won there match 7-0, Bristol Rovers finished 3rd, Northampton 4th, both finished level on points & GD, but Bristol Rovers scored more goals, & were automatically promoted instead of Northampton.