Edo Kayembe's sixth league goal of the season put Watford level with Portsmouth
Rocco Vata's 95th-minute winner earned Watford victory over Portsmouth in a controversial match at Vicarage Road.
Vata's goal deep into injury time came after Edo Kayembe had equalised with a penalty for the hosts - although replays showed contact between Kwadwo Baah and Pompey's Freddie Potts occurred outside the box.
Zak Swanson's first goal of the season had given the visitors a half-time lead.
The win moves Watford, who had Kwadwo Baah sent off after the final whistle, up to sixth in the Championship table, while Portsmouth are 21st.
The hosts started the match on the front foot and, four minutes in, Daniel Jebbison - making his first start since October - had a fantastic opportunity to open the scoring but could only shoot straight at Portsmouth keeper Nicolas Schmid when bearing down on goal one-on-one.
Pompey responded and when winger Josh Murphy found a yard of space, his excellent cross found last weekend's four-goal hero Callum Lang but he was unable to hit the target whilst on the stretch.
Ten minutes in, Pompey broke the deadlock when a poor clearance from James Morris fell to full-back Swanson, who sweetly struck a half-volley into the corner of the net to claim his first league goal since October 2022.
The visitors could have doubled their lead nine minutes later when Lang looked to get clear of the Watford defence but excellent last-ditch work from Mattie Pollock prevented the former Wigan striker from getting his shot off.
The Hornets dominated the late stages of the first half without creating anything of note. Ryan Porteous' flicked effort was the closest they came to levelling before the break.
Zak Swanson (middle) scored his first goal of the season
Twelve minutes into the second half, Baah raced down the right-hand side and was felled by Potts.
Replays showed the challenge was made just outside the box but after much deliberation, referee Geoff Eltringham decided to point to the spot, leaving the visitors dismayed.
DR Congo international Kayembe stepped up and, amongst the furore, calmly sent Schmid the wrong way to level the score.
The goal encouraged the Hornets and only a fantastic save from Schmid prevented them taking the lead.
Baah sidestepped Connor Ogilvie in the box but his left-footed effort was superbly pushed around the post by the Austrian.
Watford substitute Ryan Andrews was next to sting the palms of Schmid, with an excellent low drive, and the rebound just eluded Jebbison.
With the game looking destined to end in a stalemate, a long goal-kick from Bachmann eventually fell to Moussa Sissoko, whose heavy touch was parried out by Schmid straight to the grateful Vata, who bundled the ball home to send Vicarage Road into raptures.
Following the full-time whistle, Baah was shown a red card, seemingly for goading Pompey's fans and players, which means he will miss his side's match against Cardiff City on Sunday.
Watford's win means they maintain their unbeaten home league record this season.
They have picked up an impressive 29 points out of a possible 33 in front of their own fans.
'It's devastating' - reaction
Watford boss Tom Cleverley told BBC Three Counties Radio:
"We've got a special thing going on here (at home). That's 17 unbeaten here now.
"I was pleased that we didn't get desperate and keep lumping it forward.
"I didn't think it would be as late as it was, but I was positive that we'd get the chances we needed to win the game."
On Kwadwo Baah's red card following the full-time whistle:
"We have to admit, he deserves that one. We want to win with humility and dignity.
"People will try to goad you, and that's what he was reacting to. You can't react to that as a top professional footballer. Unfortunately we'll miss him for Sunday."
Portsmouth boss John Mousinho told BBC Radio Solent:
"I'm devastated that we lost the game - a game that we didn't deserve to lose.
"A load of emotions going through my head at the moment and the dressing room is obviously very low, because I thought we deserved to at least take a point out of the game."
Portsmouth midfielder Andre Dozzell on the award of Watford's penalty:
"I was right next to it. I saw that it was right outside the box. I've watched it back after the game and it's clearly outside the box.
"But there's some things we can't control and we are just going to have to move on."
