The win took a long time in coming as Pat Holland's side were forced to endure a torrid opening quarter of an hour, during which time Pompey took the lead.
Despite dominating play from that point on, Spurs were forced to wait until the 70 minute mark for their equaliser from Jamie Slabber and the young striker was to double his goal tally eight minutes from the end. It was an own goal that well and truly handed Spurs the initiative.
Pat Holland sent his team out in a 3-5-2 formation with Tyrie, Foster and Dobson occupying the central defensive positions. Ifil and McKie patrolled the right and left flanks respectively, with Barnett Black and Yeates in midfield. Slabber and Malcolm formed the spearhead.
After some early jostling in the opening minutes, Spurs keeper Rutherford was forced to make a dash off his line to deny Horsted a clean run on goal, but in was in the next move of the match that Pompey took the lead on five minutes.
Crawford took possession about 25 yards out, advanced towards the area and unleased a thumping shot on goal that gave Rutherford no chance.
It was an early test of character for the young Spurs and it took a last ditch challenge from Foster to deny Keene the chance to double the advantage four minutes later as he embarked on a similar run on the Spurs goal.
Pompey were certainly being bold in attack and often switched to a front three in an attempt to rattle Spurs. Crawford was breaking very quickly off the right flank to form a powerful threesome along with Keene and Horsted.
Spurs established a foothold in the game around the 15 minute mark and a Black effort from 20 yards forced home keeper Hards to save at full stretch. The move really upped the momentum in the team and midfielder Yeates was becoming more and more influential with his defence splitting passes.
Malcolm caused problems from one such pass and Black shot just over on 20 minutes. In the next move of the game, a cross from the left was met by captain Foster six yards out but his effort was superbly blocked at point-blank range by Hards.
Spurs were very much enjoying the upper hand and Slabber and Malcolm were pulling their markers around at ease from the promptings of Yeates. The football played by Spurs - in front of Glenn Hoddle - was a delight to watch at times and just reward was surely on its way...
Just before the break a Tyrie shot flashed across the goal and Pompey's defending was becoming last-ditch to say the least. Somehow, Portsmouth survived until half-time one goal to the good.
Spurs started off the second period in much the same manner as they went about their work from 15 minutes onwards - totally on top.
Just a couple of minutes in Malcolm broke down the right and fired in a shot from an angle that keeper Hards did very well to fingertip away. From the resulting corner, a flicked header by Slabber was headed off the line.
Spurs continued to pile forward and, after several promising moves broke down, Slabber got to the byline and cut the ball back to the on-rushing Barnett. The midfielder shot was deflected wide by a late, desperate challenge.
The leveller finally came 25 minutes into the second half when Yeates slipped the ball through to Slabber and the striker slotted a low shot past the advancing Hards.
Before the goal the feeling persisted that if Spurs got one a winner would soon follow - and Pompey were looking increasingly ragged.
The almost inevitable happened with 15 minutes left on the clock when Ifil dispatched an inviting cross from the right. However, it was a Pompey player who accepted the invitation and Roach's outstretched leg hooked the ball past his own keeper.
Spurs were not finished with yet and when Malcolm's shot was spilled by Hards on 82 minutes, the goal-hungry Slabber was on hand to tap home to complete an impressive win.
Swindon at home beckons in round four - and this group are well worth watching!
Spurs: Paul Rutherford, Philip Ifil, Marcel McKie, David Tyrie, Danny Foster, Ricky Dobson, Lee Barnett, Mrk Yeates, Jamie Slabber, Michael Malcolm, Jonathan Black. Subs: Mario Noto, Nicky Eyre, Daniel Perry, Tim Ford, Owen Price.
Portsmouth: Alex Hards, Callum Angus, Ben Moore, Jamie Roach, Luke Whitley, Ryan Hughes, Matthew Harfield, Gary Silk, James Crawford, James Keene, Liam Horsted. Subs: Luke Brookes, Nick Jones, Kyle Swayne, Matthew Day, Daniel Lavery.
Our under-18 youth side came from behind to register an impressive 3-1 win against Portsmouth in the third round of the FA Youth Cup at Fratton Park on Wednesday evening.