Harlequins secured a return to the Premiership with a comprehensive 65-8 win over Sedgley Park.
Quins have been able to call on former All Blacks fly-half Andrew Mehrtens
The result, coupled with closest challengers Bedford's defeat by Exeter, confirmed Quins' promotion after one season in National League One.
Quins have totally dominated the division, with their only league defeat of the season coming at Exeter in February when they lost 13-8.
They have scored 889 points so far, and conceded just 269.
Harlequins, who are coached by former Leicester boss Dean Richards, have already signed England centre Stuart Abbott and Wales winger Hal Luscombe as they look to strengthen their squad for next season.