Orient scraped three points in a gritty victory that keeps them in touch with the play-off places.
It was a game that probably won’t live long in the memory of those that braved the cold as despite controlling long periods, the O’s struggled to break down a plucky Portsmouth side scraping for their lives in League One.
A second half strike from the returning Shaun Batt was just what the O’s needed when he pounced on a sloppy pass from Dan Butler to coolly slot past Simon Eastwood from just inside the penalty area.
As in recent games, Russell Slade again rotated his squad as Kevin Lisbie dropped to the bench and Shaun Batt returned up front whilst Moses Odubajo came in for the injured Nathan Clarke as Scott Cuthbert took over the armband and returned to his familiar centre back role.
It was Pompey that started the brighter in the opening minutes as Jed Wallace tested Jamie Jones from distance but it was the O’s who had the first decent chance when Cuthbert headed over Lee Cook’s corner on seven minutes.
Orient grew into the game but it was Pompey who should have taken the lead on 22 minutes when good work from Patrick Agyemang saw him square it for an unmarked Wallace who hit a low shot that Jones did well to save with his legs.
Despite the noise from the travelling fans there, was little else to cheer in a scrappy first half as Orient controlled but rarely threatened until Cook brought the best out of Eastwood on 39 minutes when he shot from 25 yards after good work from Romain Vincelot.
Orient almost grabbed the lead soon into the second half when Batt raced through on goal but was pulled back by the referee for a foul on Ricardo Rocha. It looked harsh and was a decision that certainly incensed Russell Slade on the touchline.
The O’s did not have to wait too much longer for the lead as Pompey gift-wrapped it for them on 57 minutes. Left-back Dan Butler played an awful pass across the back four and Batt could not believe his luck as he slotted home coolly from just inside the box.
Six minutes later Orient almost returned the favour when Cuthbert misjudged a header which allowed David Connolly in on goal and the veteran got a shot off but it was scrambled away by Elliot Omozusi who had come on at centre-back for the injured Mathieu Baudry.
The introduction of Kevin Lisbie lifted the home crowd on 67 minutes and he nearly sealed the game 12 minutes later when he ran through on the left and from a tight angle forced Eastwood into a save.
Pompey showed signs of life and on 81 minutes Connolly looked sure to draw it level but he shot wide after Omozusi did brilliantly to put him under pressure.
Twice goalkeeper Simon Eastwood came up for set-plays in the final stages as Pompey put the O’s under pressure, but Orient weathered the storm and keep their season alive for a little while longer.
ORIENT: Jones; McSweeney, Cuthbert (C), Baudry (Omozusi – 62), Odubajo; Cook, James (Rowlands – 79), Vincelot, Cox; MacDonald, Batt (Lisbie – 67)
SUBS: Sawyer, Smith, Grainger (GK)
GOALS: Batt (57)
BOOKINGS: James (67) Jones (90)
PORTSMOUTH: Eastwood; Butler (Harris - 77), Rocha, Gyepes, Moutaouakil; Walker (Maloney – 69), Ertl (C), Racon, Wallace; Connolly, Agyemang
SUBS: Smith (GK), Cooper, Webster, Sodje
BOOKINGS: Maloney (73)
ATTENDANCE: 3,641 (1133)
REFEREE: Gary Sutton