The Royals battled back to draw 1-1 with Alton after 90 minutes before coming through the penalty shoot out which decided this tie 4-3 in their favour.
Normal first choice keeper Steven Mowthorpe came off the bench in the second half to replace the injured Charlie Searle, and he went on to save two Alton penalties in the shoot-out which put his side through to the last four stage of the county competition.
It was somewhat ironic that it took penalties to separate these two sides as that was the one thing the referee appeared to be reluctant to allow as this game proceeded.
Two stonewall penalties were not given to the home side during the second half - much to the amazement of both sides and on both occasions the fouls came as home players were about to roll the ball into the net.
So not only did home tempers reach boiling point when two players were judged to have dived rather than convert what looked certain goals, but in the first incident Josh Benfield was shown his second yellow card of the afternoon to reduce the Royals to ten men.
Add to that a selection of borderline offside decisions and multiple off the ball incidents ranging from blatant pushes to kicking opponents long after the ball had gone, and it was no wonder both sides were left scratching their heads by what they would have judged to have been an indifferent performance from the match officials.
This added to the drama and tension during a game in which there was nothing much between the two sides and in the first half very little in the way of chances too.
Alton went close to scoring in the opening minute when a throw in on the right was sent towards goal and Max Cunningham tried to sneak a shot low into the net but Charlie Searle blocked it behind for a corner.
On 14 minutes the ever dangerous Perry Coles cut inside from the left and hit a cross towards goal which looped up into the air and the home keeper had to tip the ball over the crossbar.
The Royals had a great chance to take the lead on 29 minutes after a corner had been cleared and the ball was then delivered back into the penalty area. The cross found Ryan Woodford unmarked but he lost track of his positioning and sent his header well wide of the goal.
On the stroke of half time the Royals broke forward down the left and the ball was played inside to Benfield, who hit a dipping shot which only just cleared the crossbar.
Alton made a lively start to the second half and on 49 minutes Owen Tanner latched on to a long through ball down the right and tried to beat Charlie Searle at his near post but the keeper got down quickly enough to block the shot at the base of his front post.
However, from the resulting corner the visitors took the lead when the ball was knocked on towards the six yard box, Alex Merrifield prodded the ball towards goal and Charlie Searle was unable to prevent it rolling across the line.
Alton should have doubled their lead on 52 minutes when Archie Markham breezed his way past the home defence and into the penalty area but he blasted his shot well over the target.
Portchester’s difficult start to the second period continued when they lost keeper Charlie Searle to injury on 56 minutes before Benfield was clearly brought down in the box as he shaped to blast the ball into the net from close range - but the referee thought he had dived and promptly showed the forward his second yellow card of the game.
Harrison Brook also then appeared to be taken out as he was about to roll his shot home but again the referee deemed he had taken a tumble rather than take what was a clear goalscoring opportunity.
Why would two home players choose to go to ground rather than take the goalscoring opportunities they had? That was a conundrum that had the majority watching at The OnSite Group Stadium stumped.
However, the introduction of substitutes Ryan Wilkins and Scott Jones gave the Royals extra impetus and they drew level on 77 minutes. The home side burst forwards down the right and when the ball was slipped to Charlie Williamson, he drove his shot home from just inside the right side of the penalty area.
Portchester almost snatched victory in the final minute of normal time when Wilkins knocked the ball on towards Marley Ridge inside the box and he tried to curl his shot into the bottom right hand corner but keeper Lewis Mees dived full stretch to his left to keep the ball out.
No one was off target with their penalties in the shoot-out as the Royals took their spot kicks first and both sides scored their first two penalties, with Woodford and Ridge making no mistakes with their spot kicks.
In round three Conor Bailey’s penalty was saved by Mees but Mowthorpe made a low save to keep Jamie Phillips’ spot kick out as well.
James Cowan and Harrison Brook both found the back of the net before Mowthorpe saved Owen Lumsden’s penalty to send the Royals through to the semi finals.