Championship rugby awaits for one of the Premiership's founding members when the game turned professional in 1996, with an uncertain future ahead for players, coaches and staff.
Worcester and Newcastle have bounced back from the second tier with immediate effect in recent seasons, while others such as Harlequins and Northampton have returned to win titles.
But clubs such as Bristol and London Welsh have found life below the Premiership harder to adapt to than expected.
What path will London Irish's future take? BBC Sport speaks to players, supporters, coaches and rugby writers to find the formula behind bouncing back from relegation.
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As recently as 2009, Irish were contesting a Premiership final at Twickenham and reached the last four of the European Cup a year earlier.
But the last three seasons have produced finishes in the bottom three, a change of ownership and changes in playing and coaching personnel.
"Although former director of rugby Brian Smith didn't enjoy the same success at the club in his second spell as he did in his first, the Australian had extensive experience of the English game," said BBC 5 live rugby reporter Chris Jones.
"He was able to comfortably avoid relegation before his abrupt departure at the start of 2015.
"Tom Coventry arrived last summer as head coach with a justifiably big reputation considering his achievements at Waikato Chiefs.
"But my understanding is that transferring coaching techniques from a Super Rugby side to a Premiership outfit wasn't a smooth process, especially given the fact Irish pretty quickly found themselves in a relegation battle.
"Coventry and his coaching team needed time to adapt to the unique nature of English rugby. The other directors of rugby involved in the basement battle - Dean Richards and Dean Ryan - are steeped in experience on this front."
Steve Jones, treasurer of the London Irish supporters' club, believes other clubs have shown Irish the way to cope with life in the Championship.
"The key is that the core of the team is kept together and our investment in the academy remains to produce young talent," he said.
"There are a lot of good players in the system that could really benefit from a year in the Championship playing regular rugby. The under-18 team that won the Academy League this season is testament to that.
"But the Championship is a hard league and Irish will find it very tough. A mixture of seasoned pros and academy graduates will be needed."
Aside from what happens on the pitch for Irish is the debate over where it happens.
Their 16-year association with Reading's Madejski Stadium could be in its final throes despite a contract that allows them to ground-share in Berkshire until the 2025-26 season.
Chief executive Bob Casey has guaranteed the Exiles will play their home games at the venue next season despite several years of dwindling attendances, but beyond is an uncertain scenario.
There are rumours that Brentford's Griffin Park and their planned new stadium at nearby Lionel Road have become favourable alternatives for the future.
"Regardless of where, for Irish to get back to the top table in England and Europe we will eventually need our own ground," Jones added.
Back row and captain Luke Narraway: "Sticking together is going to be key. We've got to eat some humble pie and learn from our mistakes.
"I'm pretty sure that most of the side, if not all of the squad, are here next year.
"In 12 months' time, we want to be sitting here looking at the following season back in the Premiership."
Scrum-half Scott Steele: "I've never been in that situation before. It's going to be about lads sticking together, not getting too caught up in it.
"I think we can't be too complacent either. We can't go down to the Championship thinking it's going to be a walk in the park.
"It's going to be a really tough league with a lot of good players and good teams."
Fly-half Greig Tonks: "I don't think there's huge changes that need to be made.
"You look at some of the results this season and there's been a lot of games that have been extremely close.
"The small margins between staying up and going down - I think we've been on the wrong side of those narrow margins, which has been very unlucky. We've had a lot of injuries.
"I think the club's still in a very good place with a great set-up. I think a lot of players will buy in to whatever happens next year.
"They'll just give it everything and I'd like to think if the boys give it everything next year, we'll come straight back up."
Prop forward Tom Court: "Everyone can point the finger in hindsight, but in essence it's one of those things where experience in the Premiership and what is required at certain times in the season is essential.
"We've got to try to retain the experienced guys in our squad.  We've seen teams like Harlequins and Northampton that have gone down and bounced back and that's what we've got to do."
John Kingston will have his hands full as the new director of rugby at Harlequins next season, but the current Quins head coach has first-hand experience of life in the Championship and how to come back at the first attempt.
They were relegated from the Premiership in 2005 and Kingston was part of the coaching staff who masterminded their immediate return.
"The big thing was we kept the nucleus of the squad together," Kingston told BBC Sport.
"There was a trust from Dean Richards (then director of rugby) coming in within the coaching group, within the players, and we stuck together. We found and evolved a style we felt worked best for us.
"We got a confidence then about what we were doing, we found what it was we believed in and it allowed us to breathe and stop accepting mediocrity and start to reach out for the stars.
"That approach and that energy has been instrumental in us being as successful as we have."
Additional reporting by Chris Jones.
After just four Premiership wins all season, London Irish have been relegated from English rugby's top flight for the first time since 1994.