Pompey brought their fine away form back to Fratton Park with a rout of Grimsby under the floodlights.
There was a touch of fortune about the first two goals, with Kyle Bennett and Danny Rose both benefiting from wicked deflections.
But it was more than luck that saw the Blues strengthen their promotion credentials, as they put their foot on the accelerator.
The points were secured with a couple more strikes either side of the interval, as first Carl Baker and then Kal Naismith got in on the fun.
Paul Cook stuck with the same side that cruised to victory against Colchester at the weekend.
And he was almost rewarded with an early goal, as Baker flashed a shot narrowly over the bar soon after kick-off.
But it was Grimsby who looked more dangerous in the opening stages and Akwasi Asante saw a shot deflected narrowly wide following an untimely slip by Matt Clarke.
They went even closer moments later, with Zak Mills’ fierce long-range drive cannoning against the post.
And David Forde was soon called into action to push another decent attempt by Asante over the crossbar.
But the Blues scored against the run of play on 12 minutes, as BENNETT tried his luck from the edge of the box and the ball took a huge deflection to loop over Mariners keeper James McKeown and into the net.
From that point on the hosts dominated and Eoin Doyle could not quite connect with Gareth Evans’ dangerous low delivery.
A back-pedalling Naismith then got on the end of another Evans cross and watched as his header flew inches past the post.
The advantage was doubled on 35 minutes, however, when Bennett dummied Evans’ pass and ROSE hit a shot that took another deflection to beat McKeown.
Pompey kept pouring forward and when Baker slipped a fine ball through to Naismith, the winger’s cut-back was diverted just behind the onrushing Eoin Doyle.
There was a blow for the Blues just before the break, though, as Bennett went down injured and had to be replaced by Gary Roberts.
But the mood soon picked up and there was a third goal in stoppage-time, with BAKER collecting Evans’ pass and beating McKeown at his near post with a ferocious finish.
Grimsby Town 0
And it got even better for the hosts just 30 seconds after the restart when McKeown failed to hold Baker’s drive and NAISMITH slotted home the loose ball.
Pompey’s players were full of confidence and lining up to shoot against a stunned opposition defence, but the next effort from Baker ended up high in the Fratton End.
Perhaps unsurprisingly, however, some of the intensity went out of their performance as the half progressed.
Evans hit a clean shot on target just past the hour mark, but this time the ball was safely held by McKeown.
Pompey were dealt another injury blow on 68 minutes when Naismith signalled to come off after hurting his hamstring, with Jamal Lowe replacing him.
That failed to dampen the hosts’ dominance, though, and McKeown dived to his left to beat away Baker’s 25-yard drive.
Lowe then whipped in a cross from the right that was just behind Eoin Doyle and the on-loan striker could only head wide.
There was a jovial feel inside the stadium, with the Fratton End asking for a song from each stand – who duly obliged.
And the Blues saw out the closing stages in complete comfort to secure a third successive victory, with a third successive clean sheet.
Pompey (4-2-3-1): Forde; Evans, Burgess, Clarke, Stevens; Rose, M.Doyle (c); Baker, Naismith (Lowe 68), Bennett (Roberts 45); E.Doyle (Chaplin 86)
Goals: Bennett 12, Rose 35, Baker 45+1, Naismith 46
Subs not used: O’Brien, T.Davies, Linganzi, Hunt
Grimsby (3-5-2): McKeown; Mills, Pearson (c), Collins; Davies, Jones (Disley 57), Maxwell, Osborne (Comley 57), Andrew; Vernon, Asante (Yussuf 81)
Subs not used: Boyce, Bolarinwa, Vose, Dyson
Referee: Mark Haywood
Attendance: 16,492 (527 away fans)