Conor Chaplin scored the first goal of his second spell at his boyhood club to set Portsmouth on course for a dominant 3-0 victory over relegation rivals West Brom.
Chaplin, who joined Pompey as a six-year-old before returning on loan from Ipswich, opened the scoring before January arrivals Millenic Alli and Ebou Adams gave them comfort.
The beleaguered Baggies have won just once in nine matches, have not won on the road since the start of October and sit just three points outside the relegation zone.
Pompey had scored late to secure a point against bitter rivals Southampton last weekend and continued the momentum with a superb first-half performance, which blew the Baggies away.
Chaplin in particular had the bit between his teeth as he fired shot after shot towards Max O'Leary's goal.
His barrage began in the second minute when he stabbed a Terry Devlin cross wide before curling straight at O'Leary from 25 yards, and then sliding across the face of goal after a fine passing move down the right.
Chaplin finally got his reward, and his long-awaited goal on his return at Pompey, in the 20th minute when Alli pulled the ball back into the area and the forward fired in with aplomb.
It ended 2,910 days since last scoring for Portsmouth before continuing his career at Coventry, Barnsley and Ipswich.
Five minutes later and the hosts doubled their lead as Alli ran beyond the West Brom backline to slide under O'Leary. It was the winger's first goal since arriving on loan from Luton two weeks ago.
West Brom were thankful for the half-time whistle, after a half in which they had only had one shot - a wayward effort off-target - and entered the Portsmouth box twice.
It was unsurprising when Eric Ramsay ripped up his game plan, made a triple substitution and switched formation from three to four at the back.
However, three minutes after the break, Pompey had a third and the hopes of a Baggies comeback dissolved.
Chaplin added an assist to his goal by threading in Adams and, despite O'Leary appearing to make a fine instinctive save, the ball bounced over the line. It further added to Adams' cult hero status, having netted the equaliser against Saints.
Mikey Johnston gave Portsmouth goalkeeper Nicolas Schmid his only piece of work for the day when a rasping shot needed tipping over.
The second half petered out, with West Brom lacking quality and Pompey taking their foot off the gas with a rescheduled match with Ipswich coming on Tuesday.
Chaplin almost added gloss to his day with a 89th-minute shot, but his effort was blocked, and Pompey made it four without defeat in the league and climbed above West Brom, and four points clear of the drop zone.
The day was soured late in the second half when assistant referee James Wilson was struck by a missile thrown from the home end.
Portsmouth's John Mousinho:
"I think it was the best performance of our season and a really important result as well. Everything we have spoken consistently over the last few months, they really put together today.
"From the first minute, we pinned them in and won the physical duels and were willing to play and go beyond. We came on top in the small moments in the game.
"That performance has been building. We have put together some decent performances and what had been missing was putting the ball in the net. That was the big difference today."
West Brom's Eric Ramsay:
"I knew the level of challenge I was coming into. I hoped the first four games had gone differently and when we got to this stage, we were in a different situation.
"The reality means I have to stay level, stay constructive and keep the group on track. I have to believe I can get more out of the group.
"It was a really tough one. It has got no easier after that result and performance, but we have to own the performance and take accountability and look inwards.
"It is difficult to say there has been a huge uplift in performance since I have been here. We are very disappointed that we haven't been able to move the group further along.
"There will be no blindly following a path without adjustment. We will take a really good look at how we move forward.
"We need to address some of the basics like fighting for second balls. We also need to look at macro and systematic factors. I certainly won't be blaming individual players."
