Chris Brunt scored one and made another on his return to The West Brom side in the 3-0 Sky Bet Championship win over Swansea at the Hawthorns.
Brunt was recalled by caretaker manager Jimmy Shan to make his first start in 11 games and gave Albion a 19th-minute lead with a free-kick.
Swansea were then handed the chance to equalise from the penalty spot five minutes before half-time when City skipper Mike Van Der Hoorn was fouled by Craig Dawson.
But Swans striker Bersant Celina lost his footing taking the penalty and could only mis-kick the ball two yards to his right.
Swansea slipped further behind when Mason Holgate scored in the 54th minute before Jay Rodriguez added a third five minutes from time as City boss Graham Potter, who played for Albion between 1997 and 2000, watched his side crash to a fifth successive away defeat.
In their first game since the dismissal of manger Darren Moore, Albion were lucky not to fall behind after 13 minutes when the post came to their rescue.
Matt Grimes fed a ball down the left wing to Wayne Routledge whose cross flew across the face of the Albion area to Connor Roberts.
His angled shot beat goalkeeper Sam Johnstone but cannoned to safety off the far post.
Albion then cashed in fully on that let-off when Brunt gave them the lead.
Swansea defender Kyle Naughton was penalised on the right wing after a crude challenge on Holgate and Brunt scored direct from the free-kick with a low cross that went through a crowded goalmouth and into the far corner of the net.
Albion almost doubled their advantage four minutes later from another Brunt free-kick but Ahmed Hegazi was inches wide with his shot.
Albion were then grateful to Johnstone for keeping their lead intact as the former Manchester United goalkeeper pulled off two stunning saves in the space of 60 seconds.
First he stopped a point-blank shot from Routledge in the 28th minute after Nathan Dyer had an effort blocked and then followed that up with a one-handed stop to deny Daniel James from close range.
Johnstone then tipped a drive from Celina over the bar after 38 minutes before the Kosovo international forward endured his penalty horror.
Albion doubled their advantage when on-loan Everton full-back Holgate scored his first goal since his arrival from Goodison Park when he headed home Brunt's right-wing corner.
Swansea's fate was then sealed by Rodriguez who pounced from 10 yards after latching on to a mis-placed clearance from Cameron Carter-Vickers.
West Brom caretaker manager Jimmy Shan: "I am delighted. Swansea posed a massive threat and Sam Johnstone's performance kept us in the game. His performances have been very, very good throughout the season.
"The instruction was one game at a time. We all know that football moves very, very quickly, and there could be an appointment in the next 24 to 48 hours. I am not too sure. But as staff, up until we know anything different, we have to make our preparations for the game against Brentford.
"I think the board had confidence in me to take the game against Swansea. I am just awaiting further instruction. The last three or four days have been surreal for me. I started coaching 18 years ago in a school playground so to fast forward to this point, there is a massive sense of pride."
Graham Potter: "It was one of those moments that you don't wish on anybody. Fair play to anyone who wants to step up and take it. It is just a horrible moment that he will have to get over and deal with.
"It is easy to mock, of course, and I am sure he will get a bit of that, but that is just life. He has the courage to take the penalty, and it is up to us to stick by him and he will grow and get better for the experience."