FREESCORING Albion stormed back to the top of the table by blitzing Bristol's seven-game unbeaten run.
The Baggies took complete control by surging two-up inside the opening 12 minutes thanks to Jerome Thomas' fourth of the season and top scorer Chris Brunt's fifth.
To their credit, City, who had lost the fewest games in the Coca-Cola Championship before today's fixture, always carried a threat and Scott Carson had to pull off a couple of fine saves to preserve Albion's cushion.
But Roberto Di Matteo's men put the game to bed at the start of the second half when Simon Cox netted a quickfire double - his second and third goals in two Hawthorns appearances.
Paul Hartley bagged a late consolation for City - but Albion were full value for their third successive win.
The hosts started the day six places and five points better off than City as Di Matteo named an unchanged team for the first time in his Hawthorns reign.
There was, however, a change on the bench where Chris Wood replaced Roman Bednar, who was ruled out by illness.
Albion were quick in the tackle from the off and typical tigerish play by Graham Dorrans in the centre circle set up a half chance for Luke Moore.
The striker raced to the edge of the box before drilling a terrific drive into the side-netting.
The Baggies then broke the deadlock in the third minute - following an incredible 60 seconds of play.
Gianni Zuiverloon had to make a goal-saving clearance under his own crossbar to deny Cole Skuse after Carson had been forced to vacate his goal to close down Nicky Maynard.
Dorrans seized on his team-mate's clearance and found Thomas on the left and the jet-heeled winger ran at the Robins defence before beating Dean Gerken all ends up with a ferocious 20-yard drive - his fourth goal in just seven games.
City almost levelled in the sixth minute when skipper Louis Carey saw his looping header from Jamie McAllister's set-piece brilliantly tipped over at full stretch by Carson.
But the Baggies looked dangerous every time they attacked - and they duly doubled their lead on 12.
Brunt timed his run to perfection as he ghosted behind the City defence and brilliantly controlled Dorrans' exquisite 40-yard throughball.
The Northern Ireland star then showed great composure to round Gerken and slot home from a tight angle.
Bristol were soon back on the attack but Maynard failed to seriously test Carson with a tame 20-yard shot.
The Baggies oozed confidence as they stroked the ball around but Carson had to pull off another fine save on 22 to deny Maynard's brilliant turn and shot in the box.
But it was Albion who should have troubled the scoresheet again moments later when City fell asleep at a free-kick.
Dorrans was completely unmarked as he charged onto Brunt's pinpoint ball into the box, only to volley wide from ten yards.
The chances kept coming in what had been an entertaining game thus far and Hartley wasn't too far away with a 20-yard free-kick which curled just wide of the right-hand post.
Albion suffered an injury setback on 30 when Joe Mattock had to be stretchered off following a clash with Maynard. He was replaced by Marek Cech.
The game entered a scrappy passage of play - which was ended in the 39th minute by a Brunt free-kick bullet, which Gerken did well to bat away.
Back came Bristol and Gonzalo Jara was in the right place at the right time to block Evander Sno's goalbound shot after Albion failed to clear a Hartley set piece.
From Hartley's ensuing corner, Marvin Elliott wasted a good chance when he directed a free header well over.
But Albion finished the first 45 on top.
The second half was only 50 seconds old when the Baggies gave themselves real breathing space by surging three up.
Zuiverloon capped his persistent play on the edge of the City box by threading through Cox and the striker's dink over Gerken was helped into the net by Carey.
Just two minutes later, incredibly, it was 4-0 when Cox underlined his predatory instincts by sliding home Thomas' pinpoint left-wing centre from six yards.
Shell-shocked City tried to regroup but Gerken was called into action again on the hour-mark when the City keeper had to dive full stretch to beat away Brunt's angled 20-yard shot.
Albion carved the visitors open again in the 65th minute when Cox fired inches wide of the far post from Zuiverloon's neat lay off in the box.
Bristol should have pulled one back seconds later when Danny Haynes raced clear of the Albion defence, only to fire wide with just Carson to beat
After Gerken had saved smartly from the dangerous Cox, City won a free-kick at the other end, which Maynard blasted well wide.
Hartley went much closer from City's next set-piece on the edge of the box, with the Scotland international forcing a fine finger-tip save from Carson.
The action swung straight to the other end and Gerken denied Brunt a second goal by brilliantly palming wide the ex-Sheffield Wednesday winger's fierce 20-yard drive.
City bagged a consolation seven minutes from time when Hartley finally found a way past Carson with a stunning 30-yard free-kick which nestled in the top corner.
Moore twice went close during the closing stages as Albion matched their biggest-ever win over City.
ALBION (4-4-2): Carson; Zuiverloon, Meite, Olsson, Mattock (Cech 30); Brunt, Jara, Dorrans (Mulumbu 57), Thomas; Moore, Cox (Koren 78). Subs not used: Kiely (gk), Wood, Martis, Teixeira.
CITY (3-5-2): Gerken; Carey, McCombe, Nyatanga; Skuse, Elliott (Johnson 78), Sno (Clarkson 78), Hartley, McAllister (Williams 17); Maynard, Haynes. Subs not used: Basso (gk), Fontaine, Sproule, Saborio.
GOALS: ALBION - Thomas (3), Brunt (12), Cox (46, 48). CITY - Hartley (83).
BOOKINGS: ALBION - Cox (simulation 78).
REFEREE: Michael Oliver (Northumberland).
ALBION STARMAN: Simon Cox.