Premiership high-fliers Wimbledon needed extra time to end plucky Portsmouth's Worthington Cup interest.
The man of the match was undoubtedly Pompey keeper Aaron Flahavan whose goalmouth heroics kept the visitors in the game.
But there was nothing even he could do as Neal Ardley's whistling drive flew past his outstretched arms in the 27th minute.
Four players were huddled over the freekick which Efan Ekoku tapped short for Ardley to strike with venom.
It was Ekoku's guile which provided Wimbledon's second in the 55th minute. Picking up a sloppy Russell Perrett header back, the Nigerian international turned before his marker to open up a run on goal. Keeping his head low, he instinctively rounded the unfortunate Flahavan who could do nothing to prevent Ekoku scoring.
But even this goal was just an equaliser. For once the giant to be killed, Wimbledon had come to the game carrying a 2-1 deficit.
When clever interpassing between Alan McLoughlin and Sammy Igoe ended in a cross straight on to Adrian Whitbread's toe, the vocal Pompey fans thought the game was won in the 19th minute.
But Wimbledon were aware of the task in hand. A string of fine Flahavan saves and the paint on the woodwork ensured an extra 30 minutes.
This was all the home side needed to book a place in the third round.
A Mark Kennedy corner found Carl Leaburn rising high above the defenders to head home from a goalmouth scramble.
Ekoku rounded off the scoring with a header from an Alan Kimble cross. But although he found the net a third time, a rare offside flag robbed him of the glory.
While the scoreline suggests an emphatic Wimbledon victory, Pompey striker John Aloisi was unlucky on several occasions not to make the net bulge.
Typically the Dons resorted to the tried and trusted tactic of pumping high balls into a crowded box.