The reason why Aberdeen weren't awarded a penalty against Celtic in extra-time of today's pulsating Scottish Cup semi-final can be revealed.

As the game headed towards full-time of the additional 30 minutes, it looked like Don Robertson pointed to the spot after a collision involving Junior Hoilett and Cameron Carter-Vickers.

The former QPR attacker made a great impact off the bench for Peter Leven's side, producing two fine crosses for for Ester Sokler and Angus MacDonald respectively to score for the Dons.

Deep into extra-time, before Aberdeen's third goal and second equaliser of the match, Hoilett went down under the challenge of Carter-Vickers in the box.

Replayed cleared showed that the American international kicked through the back of Hoilett's leg, as the Canada international nicked in ahead of the powerful defender to protect the ball. 

In real-time, it looked like referee Robertson had pointed to the spot, as the vastly outnumbered Dons fans cheered what looked a stonewall penalty.

But much to the confusion of everyone inside the national stadium, and those watching from home, a free-kick was awarded to Celtic.

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BBC's commentary team tried to make sense of the situation, deeply analysing the tackle by Carter-Vickers on Hoilett. 

However, it can be revealed that the foul in Celtic's favour was awarded in the build-up to that flashpoint. 

It's understood that Robertson spotted a foul by Hoilett on Celtic right-back Alistair Johnston inside the area, before he was then brought down by Carter-Vickers.

Once again, replays do show that there was a coming together between the pair before the penalty incident in focus, meaning it could not be awarded. 

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The first of the cup semi-finals was a classic encounter, with both teams giving as good as they got. 

Aberdeen drew first blood after only two minutes through Bojan Miovski, but Nicolas Kuhn levelled a short while later. 

James Forrest scored seconds after coming off the bench in the second half, while Sokler equalised at the death to force extra-time. 

It was then the Hoops who took the lead once again, with Matt O'Riley believing he had notched the winner. 

However, Hoilett, and indeed MacDonald had other ideas, as an almost carbon-copy of the second goal was repeated for their third of the afternoon.