Alex Gilbert scored a penalty at the death for Brentford B to send them into the Premier League Cup semi-finals after a 1-0 win against Arsenal under-21s. 

The young Bees dominated proceedings throughout but struggled to find a breakthrough in the quarter-final against the Gunners. 

Then in stoppage time Gilbert won a penalty and then picked himself up and dispatched it to send Brentford into the semi-finals. 

Progression sees Brentford down to the final four and will face one of Nottingham Forest under-21s, Fulham under-21s, or Blackburn under-21s for the chance to play in the Premier League Cup final in a memorable first time in the competition. 

Brentford had the first sight of goal when Kyreece Lisbie latched onto a loose pass on the halfway line and set Michael Olakigbe through on the goalkeeper, but his finish produced a fine stop from Hubert Graczyk. 

Late in the first half, Gilbert lined up a free-kick from deep and whipped a cross onto the head of Tristan Crama, but Graczyk once again got across his line and beat the ball away to deny the defender. 

Minutes later Gilbert sent another set piece into the danger zone, this time it was met by Fin Stevens and his header flashed just the wrong side of the post. 

The Bees were ending the opening period very strongly and could have had the lead were it not for more heroics by Graczyk when Olakigbe played a low ball across the box to pick out Gilbert, he sent the ball towards the net, but the Arsenal stopper's reactions served him well again to make the save from close range. 

Straight away in the second half, J'Neil Bennett played a slide rule pass to set Gilbert away down the side and he drilled the ball across the face of goal and Olakigbe turned into an empty net, but the flag was up for offside. 

The best chance for the young Gunners came midway through the second half as Mauro Bendeira had a free-kick and his remarkable effort looked destined for the top corner, but Matthew Cox plucked it out of the top corner and pushed it around the post. 

The decisive moment came four minutes into stoppage time at the end of the second half as Gilbert was brought down in the box by Lino Sousa, the captain then took the penalty that he had won and with his slow run-up waited for the 'keeper to move before rolling the ball into the opposite corner.