Roared on by a swathe of fans and fish, League Two Grimsby Town heaped more ignominy on sorry Southampton to reach the FA Cup quarter-finals for the first time in 84 years.
Two Gavan Holohan penalties saw Paul Hurst’s side bridge a gap of 64 league places between them and the Premier League’s bottom side.
The usual ingredients of a seismic FA Cup shock were present, including defiant acts of bravery and last-ditch defending from the visitors.
After Duje Caleta-Car pulled a goal back, Grimsby were also indebted to a tight offside decision nine minutes from time which ruled out a Theo Walcott equaliser.
Southampton were also guilty of missing a host of first-half chances while Ruben Selles, named Saints manager until the end of the season, sent out a weakened side showing nine changes from the defeat to Leeds.
The occasion, though, belonged to Grimsby, a club which reached the semi-finals twice in the 1930s but whose most famous recent FA Cup memory involved a sea of inflatable haddocks invading Wimbledon in a fifth-round tie in 1989.
The haddocks have swollen in numbers on this season’s cup run with more than 1,200 sold and in attendance at St Mary’s. They were originally banned by Southampton for this tie until a swift public relations re-think.
Grimsby’s cup run, which began in November, now numbers five victories against sides from higher divisions, so the 4,300 fans who made the near six-hour journey from east to south coast on a Wednesday, travelled with a modicum of expectation as well as hope.
That hope was almost doused four minutes in when on Adam Armstrong raced clear only to see his rising shot brilliantly saved by Max Crocombe.
An offside flag then foiled Sekou Mara after he slotted home after 18 minutes before Armstrong and Mara again wasted further opportunities.
Grimsby took the lead following a four-minute Var intervention just before half-time. Harry Clifton narrowly failed to convert a Josh Emmanuel cross, but replays showed that Lyanco had partially deflected the cross with his right hand.
Holohan calmly stroked home the penalty to give the visitors a precious lead and instigate a wild celebration of waving haddocks.
Mara ought to have equalised on the stroker of half-time but lifted his shot needlessly over the bar.
That profligacy was punished five minutes into the second half.
50 If the first penalty was justified, the second one given when Duje Caleta-Car struck out with his arm and connected with the back of Danilo Orsi was softer. Technically, the contact justified the award of a spot-kick, but not Orsi’s fall to the ground.
Holohan was anything but nonplussed, lifting his second penalty of the evening high to Alex McCarthy’s right.
Selles responded to the impending humiliation by introducing James Ward-Prowse just before the hour. It was his deep corner after 65 minutes which dropped for Caleta-Car to volley home from close range.
Substitute Walcott appeared to have spared Southampton when he turned home a Ward-Prowse free-kick nine minutes from time only for a tight offside decision to seal Grimsby’s famous passage.