Bristol Bears recorded their fifth Premiership win in a row to move into third with victory over an off-key Harlequins at Ashton Gate.
The hosts dominated the first half, with two Luke Morahan tries and 10 points off the tee from Callum Sheedy helping them to a 25-8 half-time lead.
Sheedy added another penalty for the Bears, before Gabriel Ibitoye reduced arrears for Quins out wide.
However, Quins' attack largely toiled, as the Bears stood firm.
It is the first time in their top-flight history that the Bears have enjoyed such a run in one season.
Both sides came into the game at Ashton Gate on the back of impressive wins, notably for Quins against leaders Exeter, but it was Bristol who kept up the momentum built in last week's win at Bath with a powerful display in attack and defence.
Beforehand there was talk of the back-row battle between Bristol's Nathan Hughes and Quins' Alex Dombrandt, and despite ending up on the losing side there was evidence of the latter's class - powerful running and sharp handling - and he was unfortunate to have a late try chalked off to miss out on a losing bonus point.
Bristol's strength up front was more than matched by the halves pairing of Harry Randall and Sheedy, who were sharp, lively and bright and their intent summed up the approach to the game from Pat Lam's side.
By contrast, Quins fly-half Brett Herron endured a tough afternoon for the visitors, fumbling a high kick and missing two of his three kicks at goal before he was replaced by Marcus Smith at the break.
England scrum-half Danny Care was afforded little space to work in but when he did get it right, with a sharp snipe to the right of the scrum, he exploited the numbers to put Aaron Morris through a hole for Quins' first-half score.
It took just 47 seconds to record the opening try, when a penalty advantage gave the Bears the confidence to slide from left to right and a delicious flick pass from Steven Luatua put former Wallabies wing Morahan in to score.
Morahan pounced on a loose ball to add a second, and Chris Vui finished off a series of surges close to the line after back-to-back penalties, all during a relentless first 40 minutes from the hosts.
There was far more defensive work to do in the second period for Lam's outfit as Quins finally found some field position and fluency after a scratchy start.
Despite being handed set-pieces in good positions, and working their way into decent territory, all too often there was not enough care in their execution.
Ibitoye's try, which gave Paul Gustard's side hope of a fightback, was all about pace and a good line down the left, but it was too little an impact.
Bristol Bears director of rugby Pat Lam told BBC Radio Bristol:
"It was a great start and we focused on that because when you win four in a row complacency can set in and I sensed a bit in training but the leaders dealt with it.
"The second half could have potentially been a cracking game, both teams were a bit frustrated in what we could play and couldn't play, it was a bit loose and not a great half.
"We need to be reffed, not coached through it. Ball was slow on both sides, and players play to the letter of the law. A few things were missed by both sides.
"We had a good win and we prevented them from getting a bonus point but we're gutted we didn't get the full five points (with the bonus)."
Harlequins head coach Paul Gustard:
"We had 70 per cent of the possession in the second half but blew chance after chance. They were clinical in taking theirs in the first half, but overall our defence was excellent as we limited the league's best game-breaker, Charles Piutau, to very little.
"Unfortunately our set-piece didn't function - last week against Exeter we set the benchmark but today was the polar opposite.
"Brett [Herron] missed a couple of kicks and it wasn't his day. We didn't pick Marcus in the starting line-up as he hasn't been able to train all week but he was electric when he came on."
Bristol: Piutau; Morahan, Leiua, Bedlow, Purdy; Sheedy, Randall; Thomas, Capon, Afoa, Joyce, Vui, Luatua (capt), Thomas, Hughes.
Replacements: Byrne, Woolmore, Lahiff, Holmes, Heenan, Uren, Madigan, Protheroe.
Harlequins: Morris; Northmore, Penny, Lasike, Ibitoye; Herron, Care; Lambert, Baldwin, Kerrod, Young, Symons, Chisholm, Robshaw (capt), Dombrandt.
Replacements: Musk, Auterac, Collier, Cavubati, Evans, Saunders, Smith, Saili.
Referee: Craig Maxwell-Keys.