Pompey made it a second win in the capital within a week, following an outstanding performance at high-flying Millwall.
The match at The Den was goalless at the break, but 20 seconds after the restart Gustavo Caballero’s stunning finish from the angle opened the scoring.
John Swift finished off Millenic Alli’s pull-back to make it 2-0, before Casper De Norre pulled one back on 64 minutes.
However, skipper Marlon Pack rifled home a third to complete a 3-1 victory and provide a six-point cushion above the Championship relegation zone.
And here are our Pompey player ratings...
5. Connor Ogilvie - 8
Centre-half problems, what centre-half problems. Mr Dependable has done it again. What a competitor and another superb defensive performance. | Graham Hunt/ProSportsImages
6. Zak Swanson - 8
Give him a new contract! Another superb performance at left-back from the former Arsenal man who keeps on getting better and better. What a season he is having. Superb. | Graham Hunt/ProSportsImages
7. Marlon Pack - 8
Lovely moment to see the skipper rifle in the third in front of the travelling fans. Revelling in his sudden run in the side and always uses the ball so intelligently. Don’t write him off! Photo: Graham Hunt
8. Ebou Adams - 8
Always a concern when he goes down with an apparent injury and is still a booking away from a two-game ban, such is his pivotal role in this relegation battle. Another non-stop showing from the outstanding January recruit. | Graham Hunt/ProSportsImages