Hogan smacked a shot in off the post from another fine Bacuna assist to restore their lead and then toe-poked his third from an acute angle through the legs of goalkeeper David Button.

Brandon Thomas-Asante's penalty gave the Baggies late hope after he was brought down by Dion Sanderson, but Blues held on for back-to-back wins.

The Baggies almost salvaged a seventh draw in their first nine league games when Ruddy kept out Grady Diangana's close-range header, but the visitors hung on for their first win at Albion since Bruce's time in charge of Blues, when Emile Heskey scored twice in a victory by the same 3-2 scoreline in August 2005.

Bruce's Baggies still have just one win to their name this season - and only goal difference keeps them out of the bottom three.

After traffic congestion put the kick-off back by 15 minutes, John Eustace's men made a fast start and went close inside two minutes when Troy Deeney struck a fierce shot narrowly wide.

Having scored their first away goal at the fourth attempt on Saturday, Birmingham were on the scoresheet again after 13 minutes when Hogan sent a shot across Button and into the bottom corner.

The Baggies' response was swift, Wallace forcing Ruddy to save at his near post after being found unmarked by Conor Townsend's low cross, before the winger equalised moments later.

But the hosts failed to build on their momentum, and Blues took full advantage when Bacuna's inch-perfect low cross allowed Hogan to smack a first-time shot in off the post to cap a rapid break.

Hogan took advantage of some limp defending to cut in and complete his first hat-trick since 2016 - when he helped Brentford beat Preston.

Ultimately it proved enough to secure only a second win in 11 meetings against their West Midlands rivals and leapfrog above them into 14th.

West Bromwich Albion manager Steve Bruce told BBC Radio WM:

"We never dealt with Deeney all night. The physicality of Birmingham we struggled with and it ended up in an awful display where we were second best.

"Defensively we were woeful and we'll look to do something about it - we have to.

"After performances like that, we are open to criticism. We have been waxing lyrical a few times - the last time we were here, the way we played, the time before that against Hull.

"But we throw in that hand grenade which unfortunately always seems to be around the corner. And that's what we've got to try and eradicate if possible."

Birmingham City boss John Eustace told BBC Radio WM:

"To get back-to-back wins is an incredible achievement - It's been 11 months since we've done that.

"We came here and made ourselves very difficult to play against and we also played some good exciting football."

On Scott Hogan: "He's a top player. I've worked with Scotty over the last 18 months with Ireland, I know what he can bring to the club.

"I know he can be one of the leading marksmen in the league without a shadow of doubt, he just needs that confidence. His performances throughout the season have been very good and he hasn't got the goals he's deserved."