Declan Kidney's London Irish secured promotion back to the Gallagher Premiership after recording a 46-7 victory over Richmond.
The Exiles, who were relegated from English rugby union's top flight last term, guaranteed an immediate return with a bonus-point success.
It was their 19th Championship victory of the season, with the title and promotion being clinched one game inside the distance.
Former Sale flanker TJ Ioane and wing Ben Loader each scored scored two tries, while there were also touchdowns for Albert Tuisue, Bryce Campbell, Josh McNally and Alivereti Veitokani.
Irish, whose final league game is against second-placed Ealing Trailfinders on 27 April, look set to replace Newcastle in the Premiership next season.
The Falcons are currently seven points adrift of 11th-placed Worcester, with just three games remaining.
Kidney, who had been out of the professional game since his stint as Ireland head coach came to an end in 2013, linked up with former Ulster coach Les Kiss in the summer after the Exiles had suffered relegation from the Premiership.
He's now steered back to the top flight to add to his list of achievements in the game.
Kidney led Munster to Heineken Cup wins in 2006 and 2008 before winning the Six Nations title and the Grand Slam in his first season in charge of the national side in 2009.
Ian Keatley, who moved to London Irish on loan from Munster for the remainder of the season before his switch to Benneton Rugby, started at 10 and kicked two conversions.
Irish chief executive Brian Facer said: "We have achieved our return to the top tier of English rugby, which was the only objective at the start of the season.
"I would like to congratulate and thank Declan Kidney, his coaching team and the players for working tirelessly over the last year to ensure this was possible."