A hat-trick of quick fire strikes in the first half, two of Saints' own making, were decisive for the hosts, who progress alongside Cambridge United to the knockout phases.



Harry Bunn's 13th minute opener set the tone for the tie, after he was quickest to react to a spillage from Saints stopper Harry Lewis, and turn home from close range.



Six minutes later, midfielder Harry Kyprianou was the beneficiary of another goalmouth scramble, this time caused by a Stephen McLaughlin shot, who incidentally tried to claim the goal for himself.



Kyprianou eventually stabbed the ball over the line, giving the hosts a two goal cushion, before young full-back Elvis Bwomono rounded off a smart Southend move to net his career first - and Southend's third - of the evening in the 24th minute.



The defender linked well with fellow scorer Bunn, before firing across Lewis and finding the far corner.



Radhi Jaïdi made a double switch at the break, in an attempt to change the flow of the tie. And momentarily, it did.



The visitors had a brief spell of pressure in the second period, culminating in a presentable chance for Marcus Barnes and Jonathan Afolabi, who were both inches away from latching onto a searching Yan Valery cross from the right.



The game had ultimately escaped Saints during an uncharacteristic first half, though, and despite rallying to produce a more controlled second 45 minutes, the three goal deficit was too hefty to chase down.

Southend United 13 Nathan Bishop (GK) 2 Elvis Bwomono goal 4 Luke Hyam replace Timothee Dieng (73′) 7 Michael Kightly 11 Stephen McLaughlin 16 Dru Yearwood (C) replace Jason Demetriou (82′) 23 Taylor Moore 27 Harry Kyprianou goal 28 Shawn McCoulsky 30 Harry Bunn goal replace Charlie Kelman (85′) 48 John White Substitutes 1 Mark Oxley 8 Timothee Dieng 10 Simon Cox 24 Jason Demetriou 31 Theo Robinson 32 Stephen Hendrie 34 Charlie Kelman Southampton 41 Harry Lewis 43 Yan Valery 49 Tom O'Connor (C) 51 Tyreke Johnson yellow card 54 Christoph Klarer replace Kayne Ramsay (45′) 55 Callum Slattery yellow card 58 Aaron O'Driscoll 59 Jonathan Afolabi 60 Will Smallbone 64 Nathan Tella replace Harry Hamblin (45′) yellow card 65 Marcus Barnes Substitutes 62 Jack Rose 47 Will Ferry 66 Kayne Ramsay 69 Enzo Robise 70 Harry Hamblin 73 Alex Jankewitz 75 Allan Tchaptchet