London Irish (16) 38
Kennedy 2, S Armitage, Thompstone 2, Hodgson
Bristol (7) 21
Linklater, Lemi, Eves
Bristol's Dan Ward-Smith (l) tackles Adam Thompstone in his side's defeat
Bristol were relegated from the Premiership after title-chasing London Irish confirmed the inevitable with a bonus-point victory on Saturday.
Worcester's 22-8 win over Saracens sealed their fate with two matches of the regular season remaining.
With 30 minutes left Bristol only trailed Irish 21-14 after tries by Scott Linklater and David Lemi.
But the Exiles were always on top, with Nick Kennedy and Adam Thompstone each going over twice for the hosts.
History repeated itself as the West Country club were condemned to National League One at the same venue they endured relegation in 2003, which was the last time they went down.
Bristol parted company with Richard Hill in February but although they showed signs of life under new boss Paul Hull their recent revival was far too little too late.
The Exiles' clinical finishing was crucial at the Madejski Stadium given they squandered 19 points through goalkickers Tom Homer, Delon Armitage and Seilala Mapusua.
But they retained possession for long periods and had far more firepower in attack with lock James Hudson enjoying the perfect conditions with some rampaging work in the loose.
Irish took an early lead through Tom Homer's penalty but Bristol went in front when hooker Linklater smashed his way through the Irish defence at pace to touch down, with Arscott converting.
Mike Catt only lasted a quarter of the game before hobbling off to be replaced by Peter Hewat but the Exiles scarcely noticed the influential former England fly-half's absence as they once again ran Bristol ragged.
Quick hands enabled England second row Kennedy to stroll in at the left corner to put them back in front and a Homer penalty and Steffon Armitage try gave the hosts a 16-7 half-time lead.
When play resumed they were soon back into their stride and quick hands enabled lock Kennedy to burrow over from close range out wide.
Bristol hit back with an interception try from substitute David Lemi, who plucked Seilala Mapusua's hopeful pass out of the air just 15 seconds after coming on.
But the revival was brief as four minutes later Thompstone scored and when Paul Hodgson slipped over from close range in the 73rd minute it was all over for Bristol.
Thompstone added a second and although Luke Eves ensured Bristol scored the last try of the match the game was long since up for the visitors.
London Irish coach Toby Booth:
"We want to maintain being control in our own destiny. We're in a position to do that and that's important as we found out to our peril last season. Now we are entering the month of truth.
"The reason we're not in the Heineken Cup this year is because we were depending on other results. When that happens it's an emotional time to say the least.
"In order for us to get in the top four we'll have to be much better than today because we seemed average at times."
Bristol coach Paul Hull:
"We're very, very disappointed but we knew it was a long shot.
"It's been an emotional rollercoaster over the last five weeks and I'm just proud that the players have stuck at it.
"London Irish was a game too far but at least we played right until the end."
Homer; Thompstone, D Armitage, Mapusua, Tagicakibau; Catt, Hodgson; Dermody, Paice, Skuse, Kennedy, Hudson, Danaher, S Armitage, Hala'ufia.
Richards for Homer (41), Ojo for Tagicakibau (66), Hewat for Catt (22), Coetzee for Paice (60), Lea'aetoa for Skuse (60), Thorpe for Danaher (51), Roche for Hala'ufia (71).
L Arscott; Robinson, Eves, Fatialofa, T Arscott; Barnes, Thomas; Irish, Linklater, Crompton, Sambucetti, Sidoli, R Pennycook, El Abd, Ward-Smith.
Barden for Fatialofa (73), Lemi for Barnes (49), Perry for Thomas (41), Hayes for Linklater (73), Winters for Sambucetti (48), To'oala for El Abd (29).
Nigel Owens (WRFU).