Pompey eased to victory on a chilly afternoon in Northampton to return to the top of the League One table.
It was a dominant display for the visitors and the result did not look in any doubt from the moment Sean Raggett headed them into an early lead.
Paddy Lane doubled the advantage before the break and added another goal shortly after it to leave the noisy Blues supporters full of warmth.
John Mousinho made a couple of changes from the side that won on the road at Burton earlier in the week.
One of them was enforced, with Kusini Yengi make a first league start in place of the injured Colby Bishop.
The other switch saw Lane return wide on the left, with recent signing Josh Martin moving to the bench.
Pompey showed their early intention to get forward and were causing the Cobblers plenty of problems in the opening stages.
It was not all one-way traffic, though, and Will Norris comfortably dealt with a couple of efforts from Mitch Pinnock and Sam Hoskins.
But it was the Blues who broke the deadlock on 11 minutes, when Jack Sparkes swung in a corner that was firmly nodded home by RAGGETT.
Northampton might have grabbed a quick leveller when Marc Leonard’s wide free-kick drifted towards the net, but Norris managed to keep it out.
And Pompey soon had a great chance to double their lead, with Lane stealing possession and Christian Saydee sliding a pass through to Yengi.
He rounded Max Thompson and hit a fierce angled strike that left the crossbar rattling, but the danger was not over for the hosts.
Abu Kamara sent the loose ball back into the box, where it was laid off by Saydee for Yengi, who was denied by a Jordan Willis block.
Kieron Bowie looked to hit back at the other end after possession had been turned over, but fired narrowly past the post.
Pompey were proving to be more ruthless and did go further ahead on 26 minutes, when Saydee found LANE with a fine pass.
Thompson came out to try to deal with it, but the Northern Ireland international got there first and neatly dinked the ball over the keeper.
Saydee soon made himself an opening after bulldozing his way through three challenges before eventually seeing his effort blocked by Willis.
Half Time: Northampton 0 Pompey 2
Any thoughts of the visitors protecting their two-goal advantage vanished within three minutes of the restart.
Northampton were again punished for some sloppy play, as Saydee nipped in to steal the ball and find the impressive Alex Robertson.
His cross was met by LANE in the box, with the winger chesting the ball down and slotting it home with his left foot.
The Cobblers looked to apply some pressure of their own, with the Blues responding by calming things down and keeping possession.
It proving to be all rather easy and a Robertson corner caused further problems, but nobody in a packed box could force the ball over the line.
The Australian midfielder then released Lane with a neat pass, although there was not enough power on the shot to properly trouble Thompson.
Mousinho made a change on 72 minutes, with Saydee serenaded by the travelling faithful as he made way for Terry Devlin.
The chances kept coming and Raggett swept a fine pass out to Sparkes, whose deep cross was just out of reach for both Yengi and Lane.
A late double switch saw Lane and Robertson given a breather, as Martin and Ben Stevenson were brought on.
Gavin Whyte also replaced Kamara and the Blues were in cruise control for the closing stages to continue their fine form on the road.
Northampton (4-2-3-1): Thompson; McGowan (c), Willis (Guthrie 46), Sherring, Brough; Sowerby (Hondermarck 77), McWilliams; Pinnock (Appéré 46), Leonard, Hoskins; Bowie
Booked: Bowie
Subs not used: Dadge, Monthé, Haynes, Simpson
Pompey (4-2-3-1): Norris; Rafferty, Raggett, Shaughnessy, Sparkes; Robertson (Stevenson 84), Pack (c); Kamara (Whyte 89), Saydee (Devlin 72), Lane (Martin 84); Yengi
Goals: Raggett 11, Lane 26, 48
Booked: Norris
Subs not used: Schofield, Swanson, Towler
Referee: Darren Drysdale
Attendance: 7,215 (1,454 Pompey fans)