Gavin Brennan’s first-half penalty kick decided a hugely controversial Louth derby in the FAI Ford Cup semi-final as Drogheda United held on to beat nine-man Dundalk 1-0 at Hunky Dorys Park.

It was an entertaining, end-to-end contest for 25 minutes until Darren Meenan got his marching orders from referee Anthony Buttimer for an innocuous challenge on Paul O’Conor, and four minutes later Chris Shields was dismissed for scything down Declan O’Brien in the box.

Gavin Brennan scored the resulting penalty to give Drogheda the lead on the half-hour.

For the remaining 60 minutes, however, the Boynesiders struggled to break down a resolute nine-man Dundalk and substitute Tiarnan Mulvenna nearly earned the visitors a replay in the 85th minute, only for Drogs keeper Micheal Schlingermann to make a fine diving save.

Dundalk right-back Mark Rossiter failed to recover from a knock and was replaced by John Sullivan in Dundalk’s starting XI, but otherwise the sides lined out as expected and it was Drogheda who threatened first when Ryan Brennan had a header deflected over the bar.

Then his brother Gavin fired a 35-yard free kick a yard over Peter Cherrie’s crossbar.

But the Lilywhites responded with two much clearer opportunities, starting with a free header for Brian Gartland which sailed harmlessly wide in the 11th minute.

And Drogheda had a lucky escape when their keeper Micheal Schlingermann ill-advisedly came off his line to meet Dane Massey’s cross, and Stephen O’Donnell beat the netminder in air but could not divert the ball to the empty net.

Past the 20-minute mark Alan Byrne forced a save from Cherrie with a downward header and the keeper then held an O’Conor drive comfortably.

But there was no hint of the controversy that was about to unfold as two Dundalk players were red-carded in the space of four minutes.

First, Darren Meenan was given his marching orders for a tackle on O’Conor that surely merited a yellow card at most, and hardly had Dundalk’s anger begun to wane when Shields tripped O’Brien from behind in the penalty area and was dismissed by Mr Buttimer – even though there seemed to be a covering defender.

Gavin Brennan duly converted the resulting spot kick and Drogheda had the lead against nine men.

However, the Lilywhites dug deep coming up to half-time as the Boynesiders sat back, and it took a vital block by Shane Grimes to deny O’Donnell an unlikely equaliser in the 43rd minute.

Stephen Kenny and members of his management team tried to confront Buttimer shortly after the half-time whistle and both assistant boss Vinny Perth and fitness coach Graham Byrne were dismissed during the interval.

But Dundalk were not going to throw in the towel and they defended resolutely in the second half against a Drogheda side who seemed uncertain how to approach the game.

Other than a driven shot to the near post by Gavin Brennan which Cherrie pushed away for a corner, the Lilywhites did not look like conceding until huge gaps began to appear in the closing 10 minutes.

Dundalk sub Mulvenna had a great chance to level for the nine men on 85 minutes when he burst clear of Alan McNally and drew a great save from Schlingermann.

But a minute later it was Cherrie performing heroics to keep out a Grimes piledriver and Drogheda held out for the remaining time to seal their place in the Aviva Stadium showpiece.

DROGHEDA UTD: M Schlingermann; M Daly, A McNally, D Prendergast, S Grimes; A Byrne; D Cassidy, P O’Conor (P Hynes 61), R Brennan, G Brennan; D O’Brien.

Subs not used: G Holohan, C Brady, G Rusk, E Foley, J Marks, G Sava.

DUNDALK: P Cherrie; J Sullivan (V Faherty 75), B Gartland, A Boyle, D Massey; D Meenan, C Shields, R Towell, S O’Donnell; P Hoban (J Mountney 38), K Byrne (T Mulvenna 66).

Subs not used: J Dillon, S Kelly, N Murphy, C Winn.

Referee: A Buttimer (Cork).