Pompey produced a performance of attacking excellence to steamroller Northampton at a jubilant Fratton Park.
Early goals from Connor Ogilvie and Paddy Lane were a sign of the mood that the hosts were in and they could even afford to see Colby Bishop’s penalty saved.
There were concerns when Tom McIntyre was bizarrely sent off for a clean challenge after the break, but they soon evaporated.
A thumping finish from Lane effectively wrapped up the contest before Callum Lang further endeared himself to the faithful with a close-range volley.
The Cobblers struck late on through Marc Leonard, but that failed to dampen south coast spirits following a comprehensive Blues display.
John Mousinho made four changes from the side that were held to a draw at Oxford earlier in the week.
Lang came off the bench to score that night and was handed a full debut alongside fellow January arrival McIntyre.
Tom Lowery and a fit-again Joe Rafferty also returned to the starting line-up, with Joe Morrell and Terry Devlin missing out through injury.
Sean Raggett and Abu Kamara dropped to the bench, where they were joined by deadline day capture Owen Moxon.
Pompey made a blistering start and refused to let their opponents settle, surging forward whenever possible.
They thought the deadlock had been broken after Ogilvie cut in from the left and hit a low shot that Lee Burge could only parry.
The loose ball was tucked away by Bishop, but his celebrations were quickly cut shot by an offside flag.
Northampton were only granted a quick reprieve, however, as the hosts did take the lead just a few seconds later.
Marlon Pack swung a free-kick into the box from the right and OGILVIE found space to convert it with a stooping header.
There was no chance of the Blues sitting back and they looked to keep increasing pressure on the Cobblers.
It paid off handsomely on 16 minutes after impressive skipper Pack played a superb long pass up the pitch.
That sent LANE racing away and the Northern Ireland international cut in from the right before using his left foot to bend the ball into the net.
Still the chances kept coming and when attempts to clear Pack’s centre failed, Patrick Brough did well to stop Ogilvie from finding the target.
Lane then sent in a dangerous low delivery from the right that a sliding Bishop could not quite get on the end of.
Bishop had an even better chance to increase the lead just before the break when Myles Peart-Harris was shoved to the turf by Harvey Lintott.
Referee Sam Purkiss pointed to the spot, but the striker’s penalty was saved by Burge low to the keeper’s left.
Half Time: Pompey 2 Northampton 0
Pompey continued to look in control once the action restarted, as they passed the ball around with ease.
But they were dealt a blow on 54 minutes after a decision from Purkiss that nobody inside Fratton Park could quite believe.
McIntyre went in for a challenge with Mitch Pinnock and appeared to win the ball cleanly, with minimal contact made with the Northampton attacker.
But after lengthy discussions with his assistant on the sidelines, the official decided to brandish a red card, resulting in a mixture of frustration and bemusement around the ground.
With defensive resources depleted, Mousinho moved to shore things up by replacing Peart-Harris with Raggett.
And the Blues quickly put the setback behind them to strengthen their advantage after Lang had stolen possession from a Cobblers free-kick.
He surged up the pitch and laid the ball off for LANE, who took an excellent first touch before smashing the ball home from the edge of the box.
There was a chance for the visitors to hit back after a spot of pinball in the area, but blue-shirted players bravely threw themselves in the path of shots.
Despite holding the numerical advantage, Northampton were still on the back foot and it took a clearance from Brough to stop Lintott heading Lane’s corner into his own net.
Pompey did have a fourth on 71 minutes, though, and again Pack played a key role in the goal being scored.
His free-kick was nodded towards the back post by Ogilvie and LANG was waiting to volley it into the net.
Mousinho rested some legs soon after, with Lane and Lang afforded standing ovations as they made way for Kamara and Jack Sparkes.
Will Norris had enjoyed a fairly quiet afternoon, but had to be alert when Kieron Bowie raced into the box, narrowing the angle to deny the striker.
And with the contest petering out, there was a chance to catch a glimpse of Moxon as he came on for Tom Lowery.
Northampton had been outplayed, although they at least managed to grab a late consolation, just after Norris had made a fine save to deny Louis Appéré.
When the resulting corner was only partially cleared, Leonard hit a fine 20-yard strike that flew in off the underside of the crossbar.
That was a mere footnote, however, as the Blues saw out 10 minutes of stoppage-time to seal a resounding success.
Pompey (4-2-3-1): Norris; Rafferty, Shaughnessy, McIntyre, Ogilvie; Lowery (Moxon 84), Pack (c); Lane (Kamara 75), Lang (Sparkes 75), Peart-Harris (Raggett 57); Bishop
Goals: Ogilvie 7, Lane 16, 58, Lang 71
Sent off: McIntyre
Booked: Sparkes
Subs not used: Macey, Martin, Saydee
Northampton (3-4-1-2): Burge; Willis (Springett 69), Guthrie (c), Monthé; Lintott (Fox 79), Hondermarck, Leonard, Brough; Pinnock; Bowie (Simpson 79), Hoskins (Appéré 40)
Goals: Leonard 89
Booked: Guthrie
Subs not used: Moulden, Sherring, Gape
Referee: Sam Purkiss
Attendance: 19,245 (756 away fans)