Leicester Tigers' victory over Wasps on the final day of the regular Gallagher Premiership season ensured they became the first Premiership club to go through a season on top of the table after every round.
Steve Borthwick's side will now face their East Midlands rivals Northampton Saints in the semi-finals and move into that match off the back of a 20-10 win over Wasps.
Tries from Guy Porter and Freddie Steward completed a clean sweep of home league victories at Mattioli Woods Welford Road for the first time in 20 years.
Defeat for Wasps, whose only try came from a late Will Porter breakaway, ended their slim hopes of gaining qualification for the Heineken Champions Cup, as London Irish finished above them in eighth position.
Leicester's semi-final opponents - Northampton Saints - also go into the knockout stages off the back of a victory.
Tommy Freeman showcased his burgeoning talent by scoring a hat-trick in Saints' 65-26 thumping of Newcastle Falcons.
Saints scored 10 tries during an extremely open contest at Franklin's Gardens and it means they are into the semi-finals for the first time in three years.
It was not the finale Falcons' director of rugby Dean Richards was looking for, as he ended a decade in charge. His side also had Sean Robinson sent off during the contest in Northampton.
Saracens, whose women's team claimed a third Premier 15s title in four years on Friday, will host Harlequins in the other Gallagher Premiership semi-final next weekend.
Mark McCall decided to make wholesale changes to their starting line-up and rested his key men in Round 26, including England internationals like Owen Farrell, Maro Itoje, Jamie George, Billy Vunipola and Elliot Daly.
Away from home, Saracens fell to to their second-heaviest defeat in Premiership history, as Gloucester Rugby were superior in all departments and prevailed 54-7 at Kingsholm.
The Cherry and Whites' first-half tries came from hooker Jack Singleton, flanker Jordy Reid and full-back Santiago Carreras.
Further second-half tries were added by former Saracens player Singleton, replacement hooker Santiago Socino, Ollie Thorley, his fellow wing Louis Rees-Zammit and flanker Jack Clement, while fly-half Adam Hastings kicked seven conversions.
A Max Malins try and a Manu Vunipola conversion provided Saracens' solitary points.
Harlequins travelled to Devon for their Round 26 clash with Exeter Chiefs and were part of an extremely high-scoring encounter.
A record crowd of 14,876 at Sandy Park saw Chiefs finish their season in style by triumphing 47-38 in a 13-try thriller.
Despite being guaranteed a third-place finish, Quins decided to field a full-strength line-up, no doubt in order to remain battle-hardened ahead of their play-off.
Exeter's tries came from Jonny Gray, Stuart Hogg, Ian Whitten, Jack Nowell, Marcus Street, Sam Maunder and Joe Simmonds, who added six conversions.
Even with their try-scoring bonus point, Exeter still finished seventh in the Premiership table and it is the first time they have missed out on a play-off spot since 2015.
Will Evans, Joe Marchant, Aaron Morris, Louis Lynagh, Lewis Gjaltema and Tyrone Green all crossed the whitewash for Harlequins. Marcus Smith converted three of their tries and Tommy Allan one.
In the other Round 26 encounter, Sale Sharks marked the departures of South Africa duo Faf De Klerk and Lood De Jager in perfect fashion as they recorded a 42-19 victory over Bristol Bears at the AJ Bell Stadium.
De Klerk has become a fans' favourite, turning out consistently-excellent performances over the past five years, while De Jager has been a physically imposing athlete throughout his time with the Sharks.
Injuries have hampered the Springbok lock's Sale career but the South African duo were at their best, as the Sharks hammered a forlorn Bristol team.
Sale dominated the first half, touching down four times through Tom Roebuck, Akker van der Merwe and Cobus Wiese's brace.
Toby Fricker crossed the whitewash and Nathan Hughes scored a double in the second period to hand Bristol a little consolation, but Sale managed two of their own via Dan Du Preez and Arron Reed.
In the other Round 26 match, Worcester Warriors beat Bath Rugby 43-27 and condemned Bath to a bottom-of-the-table finish.
Jamie Shillcock led the way with a hat-trick for the hosts, who also saw Kyle Hatherell, Gareth Simpson and Joe Batley cross.
A Will Muir double and Will Stuart's score put Bath in control in the first half but the Warriors fought back to leapfrog their visitors in the basement battle.