Pompey Academy battled from behind to win 2-1 at Swindon and replace their hosts at the top of the Youth Alliance League table.
A below-par performance in the first half ensured that it was the Robins leading through Wynn Davis’ strike at the interval.
But the Blues levelled when Dan Gifford (pictured) latched onto Spencer Spurway’s long clearance and fired home.
And a cross from substitute David Setters was converted by Harvey Hughes at the back post to complete the turnaround.
Assistant professional development phase coach James Barlow said: “We’d worked hard in training on gaining control of possession past the halfway line.
“But we were quite shaky to start with and weren’t really able to settle against Swindon’s direct style of play.
"To fight back from going behind in difficult, hot conditions was great and the boys stuck together throughout."
“We had to show a lot of character after going in behind at the break and eventually came through that spell.
“There were conversations about whether to change, but we stuck with it and the lads were able to find solutions.
“We haven’t really seen David play for around six months now because of injury, so it was pleasing to see him come on and make an impact.
“To fight back from going behind in difficult, hot conditions was great and the boys stuck together throughout.
“They showed an abundance of maturity, although there’s still a lot for us to work on at this early stage of the season.”
Pompey: Steward; Kaba, Spurway, Traynor (Setters 60); Fox, Fuller, Simpson (Aston 71), Hughes; Payce; Gifford, Trialist