Bristol Bears' brilliant second-half display helped blow away rivals Gloucester and secure a first Premiership win since November.
Five Bears penalties to three in a try-less opening 40, slotted by Callum Sheedy and Owen Williams respectively, separated the two sides at the break.
Henry Purdy brushed over for Bears' first try after half-time, followed by Luke Morahan and Mat Protheroe scores.
Freddie Clarke crossed late on for a Cherry and White consolation.
Goal-kicking fly-half Williams' first start for a year after a knee injury was one of the bright spots for Gloucester head coach Johan Ackermann, who saw his side miss the chance to keep up pressure on the top two with defeat.
The enthusiasm for this West Country derby was reflected in the size of crowd, as 18,779 fans packed into Ashton Gate to create a buzzing atmosphere.
Bears' patience bears fruit
Patience was at the heart of Pat Lam's side's victory, as they were allowed to dominate possession without genuinely striking the Gloucester defence in the first half and then found chinks in the visitors' armour in the second 40.
They straightened things up after the break, utilising the bulldozing Nathan Hughes to great effect, while Sheedy and Harry Randall sniped cleverly behind.
With Gloucester's strike weapons out wide kept quiet, including recent Wales call-up Louis Rees-Zammit, Bristol controlled the game and looked comfortable for large periods.
The gameplan from the visitors shepherded the Bears into lateral movement, limited them to pot-shots from Sheedy's boot and then punished Bristol's over-enthusiasm at the restarts - which twice saw Dave Attwood become isolated at the ruck - to keep themselves in the contest.
Bristol's attacking tweaks eventually unlocked the door through Purdy's score against his old club, and the Bears streaked clear when Morahan and Protheroe profited out wide after defensive softening-up.
Clarke's score helped give the scoreline a more favourable shade for Gloucester but came too late to turn the tide.
Bristol Bears director of rugby Pat Lam told BBC Radio Bristol:
"I'm very pleased for Henry, he's a quality rugby player, very intelligent and understands the game. He showed us coaches that he's got a really good understanding, we didn't hesitate to put him out there.
"We controlled possession and we controlled territory which takes its toll eventually, we knew the stats show they're extremely strong in the second half this year.
"We talked at half-time that they needed to be prepared to lift our efforts another level and the boys did that. I was frustrated with the last five minutes, we should have come home strong.
"The forward pack, that's the key, to play the game you need to earn the right to go forward, going off front-foot ball. Those are things we weren't doing previously."
Gloucester head coach Johan Ackermann told BBC Radio Gloucestershire:
"For me it's massively disappointing, the whole performance, but we expected to have more ball, more composure on our first-phase attack, but we never saw the ball.
"The little ball we had we turned over or lost in contact, and gave it to them to play again. Eventually they had 70-plus percent possession and territory and defensively it took a lot out of us.
"The penalties at the moment are hampering us every game, their team has opportunity to build the scoreboard. It's a difficult one but it's not a constant in a same area.
"If you go above a certain number of penalties it's always going to be tough to win."
Bristol Bears: Morahan; Purdy, O'Conor, Bedlow, Leiua; Sheedy, Randall; Woolmore, Malton, Afoa, Attwood, Vui, Luatua (capt), Thomas, Hughes.
Replacements: Capon, Dawe, Thiede, Holmes, Heenan, Uren, Lloyd, Protheroe.
Gloucester: Woodward; Marshall, Harris, Atkinson, Rees-Zammit; Williams, Simpson; Rapava-Ruskin, Marais, Balmain, Craig, Mostert, Ackermann, Ludlow (capt), Morgan.
Replacements: Gleave, Hohneck, Knight, Clarke, Polledri, Braley, Twelvetrees, Banahan.