Pompey secured promotion to League One with three games to spare after winning at Notts County.
The result – coupled with Luton’s failure to beat Mansfield – ensured the Blues ended their four-season exile in the fourth tier.
Gareth Evans fired them into the lead from the penalty spot, only for Jorge Grant to level after the break.
But Jamal Lowe came off the bench to add two goals and the referee’s final whistle was the cue for the party to really begin.
Paul Cook made two enforced changes from the side that drew with Plymouth on Good Friday.
With Matt Clarke and Danny Rose both nursing knocks, it opened up spaces in the starting 11 for Jack Whatmough and Amine Linganzi.
The sides emerged to a sea of ticker tape from the 4,366 travelling fans crammed into the Jimmy Sirrel Stand to the side of the pitch.
And although there was a slow start to proceedings on the pitch, there was certainly a jovial atmosphere off it.
Pompey supporters were in fine voice as they sang the Herman’s Hermits hit I’m Into Something Good, with the lyrics adjusted to reveal they had promotion on their minds.
It was the visitors who looked more threatening in the early stages and Gary Roberts was blocked off after being slipped through by Kal Naismith.
And they were awarded a penalty when Michael Doyle’s incisive pass released Naismith, the stand-in striker burst into the box and former Blues defender Richard Duffy was drawn into making a clumsy challenge.
Referee Graham Salisbury had a simple decision to make and EVANS stepped up to coolly send County keeper Adam Collin the wrong way from the spot.
Pompey fans had further reason to celebrate soon after, when it emerged that Luton had fallen behind at Mansfield.
But the visitors were certainly not home and dry, with Jon Stead not able to get a decent connection on Adam Campbell’s cross and the ball flying into David Forde’s arms.
A free-kick then led to a scramble in the Blues box before Carl Baker was eventually able to hack to safety.
There were certainly not an abundance of clear-cut openings at either end of the pitch, however, as the half drifted along.
Forde tried to launch an attack when he claimed a cross and picked out Naismith with a fine clearance, but the Scotsman was crowded out.
Notts County 0
The hosts looked more lively once the game restarted and Matt Tootle found Campbell unmarked in the box, only for the forward to volley over the bar.
And there was more reason to feel tense, as a couple of goals were soon scored to put Pompey’s promotion party on ice.
First news began to filter through that Luton had equalised at Field Mill and then Notts County grabbed a leveller of their own.
Elliott Hewitt sent a lofted pass into the area and Grant met it to send a fine curling finish past Forde’s grasp and into the net.
A more traditional striking option was introduced for the visitors just past the hour mark, as Roberts made way for Conor Chaplin.
There had not been much pressure applied by Pompey since the restart, although Baker’s incisive pass found Enda Stevens down the left and his low centre was just behind Kyle Bennett.
And Baker could then only chip the ball into Collin’s arms after struggling to dig the ball out on the edge of the box.
The visitors were pushing for another goal and when a couple of fine passes from Baker and Chaplin created a chance for Naismith, his angled drive was kept out by the feet of Collin.
Another attacking player was thrown into the mix on 69 minutes, with Baker withdrawn for Lowe.
Pompey were suddenly looking a real threat and the lively Bennett surged forward before seeing his stinging drive superbly tipped over by Collin.
And their pressure paid off on 77 minutes when LOWE collected Naismith’s pass, cut onto his right foot and curled home a shot.
Home fans thought they should have had a penalty soon after when Mark Yeates’ cross appeared to strike the hand of Christian Burgess, although there did not look to be much intent from the defender.
And Lowe made a vital block to deny Rob Milsom as fingernails were chewed among the expectant away fans.
But they had cause to celebrate late on when LOWE burst clear and confidently lifted home his second goal of the afternoon.
There was also a roar when those supporters learned that it had finished all square between Mansfield and Luton.
And when Salisbury blew the final whistle, it was the cue for Pompey fans to pour onto the pitch and mob their heroes.
Three more games and then the Blues’ League Two stay is at an end.
Notts County (4-2-3-1): Collin; Tootle, Duffy, Hollis, Bola; O’Connor (c) (Yeates 45+1), Milson; Hewitt, Grant, A.Campbell (T.Campbell 75); Stead
Goals: Grant 51
Booked: O’Connor, Bola
Subs not used: Searson-Smithard, Dickinson, Clackstone, Smith, Forte
Pompey (4-2-3-1): Forde; Evans, Burgess, Whatmough, Stevens; Linganzi, M.Doyle (c); Baker (Lowe 69), Roberts (Chaplin 62), Bennett (Aborah 90+2); Naismith
Goals: Evans 14 (pen), Lowe 77, 90
Booked: Linganzi, Chaplin, Naismith
Subs not used: O’Brien, Talbot, T.Davies, Main
Referee: Graham Salisbury
Attendance: 12,184 (4,366 Pompey fans)