Pompey collected their first victory of the season thanks to a late Gary Roberts brace against Colchester.
The visitors did not offer much in attack, but looked like they might be leaving the south coast with a point after frustrating the Blues.
Roberts won and scored a penalty to relieve the tension, however, and then grabbed a second moments later to secure all three points.
Paul Cook made one change from the side that were beaten at Morecambe earlier in the week.
That came up front, where Michael Smith missed out completely and was replaced by Curtis Main.
The blustery conditions made things difficult for both sides early on, with several passes going astray.
But it was the Blues who settled the quickest and carved out the majority of the chances before the break.
The first of those arrived after six minutes when Roberts swung in a cross that Main flicked narrowly past the post.
Kyle Bennett then played a neat one-two with Roberts down the left, only to see his low delivery cleared by Doug Loft.
Pompey were dominating possession without really troubling United keeper Sam Walker and Carl Baker headed wide after being found in the box.
The hosts were winning plenty of corners, however, and one from Bennett caused a scramble in the box before eventually being hacked clear.
Despite being penned back in their own half, Colchester looked dangerous on the break, although David Forde was not exactly being overworked.
It was the Blues still doing most of the attacking, however, and they started to put more pressure on the opposition back-line as the break drew closer.
Their best chance came on 40 minutes and it was Roberts who once again started the move.
He cut the ball back for Main, but Walker made a fine save to keep out the striker’s shot and then used his feet to stop Danny Rose from converting the loose ball.
Colchester United 0
Pompey started the second half on the front foot and, with Main waiting to pounce, Walker had to quickly recover after fumbling Baker’s shot.
The keeper looked more assured moments later, however, when he gathered a Roberts cross-shot at his near post.
But the chances began to dry up and Cook attempted to inject some fresh impetus into proceedings with a double switch.
The crowd had been calling for Conor Chaplin and he was brought on alongside Noel Hunt, with Bennett and Main making way.
Walker immediately came for – and missed – a Roberts corner, but got away with it as there was no-one at the far post to capitalise.
Forde might have been a virtual spectator, but he had not let his concentration slip and made a key save on 70 minutes to deny Craig Slater.
Chaplin did well soon after, beating his man and chipping the ball up to the far post, where it was just out of reach for a stretching Baker.
But the Blues did finally break the deadlock on 80 minutes, thanks to a penalty that was won and converted by ROBERTS.
He was clearly tripped inside the box by Drey Wright before stepping up and sliding the ball straight down the middle.
And the Fratton faithful were soon celebrating a second goal when ROBERTS raced onto a fine pass from Chaplin.
He just about beat the onrushing Walker to the ball, which looped up and landed in the net to double the Blues’ advantage.
Colchester tried to find a route back into the game, but Forde made a decent double save to deny Chris Porter and Doug Loft late on and preserve the clean sheet.
Pompey (4-2-3-1): Forde; Talbot, Burgess, Barton, Stevens; Rose (Linganzi 86), Doyle (c); Baker, Roberts, Bennett (Hunt 62); Main (Chaplin 62)
Goals: Roberts 80 (pen), 84
Subs not used: O’Brien, T.Davies, Evans, Lalkovic
Colchester (4-2-3-1): Walker; Brindley, Eastman, Prosser (c), Kinsella; Lapslie, Loft; Guthrie (Wright 59), Slater (Bonne 82), Dickenson; Johnstone (Porter 71)
Booked: Guthrie, Kinsella
Subs not used: Bransgrove, Wynter, Vincent-Young, Szmodics
Referee: Charles Breakspear
Attendance: 15,967 (442 away fans)