Gavan Holohan converted two penalties as League Two side Grimsby dumped Premier League strugglers Southampton out of the FA Cup with a shock 2-1 win at St Mary’s.

Midfielder Holohan capitalised on moments of madness from Saints pair Lyanco and Duje Caleta-Car to fire the Mariners into the quarter-finals of the competition for the first time since the Second World War.

Croatia defender Caleta-Car atoned for his mistake by halving the deficit for the top-flight’s bottom club with 25 minutes to go.

But the 1976 FA Cup winners could not prevent another major setback of a miserable season as they crashed out at the hands of the lowest-ranked side remaining in the tournament.

Southampton substitute Theo Walcott thought he had equalised 10 minutes from time, only to be deemed offside following a VAR review, before the stunned hosts were loudly booed off.

Grimsby arrived on the south coast seeking to reach the last eight of the cup competition for the first time since 1939 and backed by more than 4,200 boisterous fans waving inflatable fish.

The Mariners faced a Southampton side showing nine alterations from Saturday’s damaging 1-0 defeat at Leeds and with more home wins in the cup than the top flight this term.

Saints’ much-changed side dominated possession but rarely threatened as they tried to inspire a sparse and subdued home crowd.

Sekou Mara saw an 18th-minute finish disallowed for offside against creator Moussa Djenepo and later scuffed a tame shot at Town goalkeeper Max Crocombe, while Mislav Orsic curled narrowly wide and Carlos Alcaraz fluffed a diving header attempt.

A largely forgettable first half of few chances burst into life just before the break as Grimsby benefited from a lengthy VAR check to edge ahead when Saints defender Lyanco inexplicably handled Joshua Emmanuel’s cross as he misjudged a header under little pressure.

Referee Thomas Bramall watched replays on the pitchside monitor and, around six minutes after the initial incident, Holohan coolly stepped up to send Alex McCarthy the wrong way from the spot and spark mayhem among the travelling hordes.

Saints boss Ruben Selles would have been desperate for a swift response from his side but his half-time team talk was quickly undermined by a farcical moment of petulance.

After snuffing out the danger, Caleta-Car foolishly slapped Danilo Orsi in the back inside the 18-yard box, prompting match official Bramall to point to the spot for a second time.

Irishman Holohan once again took responsibility, coolly dispatching a rising effort into the left corner beyond the fingertips of McCarthy.

Spaniard Selles responded to the perilous position by introducing captain James Ward-Prowse and Samuel Edozie from the bench.

Ward-Prowse sparked hope of a fightback by delivering an inviting in-swinging corner for the unmarked Caleta-Car to make amends for his earlier error of judgement by volleying home unmarked.

Saints piled forward in search of an equaliser and were almost caught on the counter-attack when John McAtee burst clear from halfway before overrunning the ball at the crucial moment.

Extra-time then looked on the cards when Walcott spun to convert following a quick Ward-Prowse free-kick into the box.

But Paul Hurst’s men received a reprieve from Stockley Park, leaving the raucous away end to revel in a memorable evening out ahead of a 240-mile journey home, while Saints were jeered off in shame as attention turns back to their scrap for survival.