 Complete the following phrase:  With the advent of professionalism at around the same time, the amateur teams quickly faded from prominence in the competition. The leading professional clubs formed The Football League in 1888. Since then, one non-league team has won the cup. Tottenham Hotspur, then of the Southern League, defeated Sheffield United of The Football League to win the 1901 final. A year later Sheffield United returned to the final and won the cup, which then remained in the hands of Northern and Midland clubs until Tottenham won it again in 1921. In 