Rehanne Skinner made a double change at the break as Endo and Ueki made way for Anouk Denton and Asseyi, and the substitutes caused havoc inside the opening exchanges of the second half.
First the France international drove down the left with pace and trickery, putting a low cross to the front post that Paví could only get a deft touch on. Then it was Denton’s turn to get to the byline and she flashed a venomous ball across goal that no one in Claret and Blue could get a touch on.
We shortly turned to the bench again, sending on Martinez for Nyström. The Germany U23 international won us a corner down the right almost instantly, and it was from the resulting set-piece that we found the breakthrough. Hanshaw whipped in a pinpoint delivery and there was Asseyi to flick the ball beyond Stenson in the Southampton goal.
It was not long before Martinez got on the scoresheet though. She flicked on a long throw from Belloumou into Denton’s path. The Young Lioness scrambled for the ball in the area and it eventually landed at the feet of Martinez, who rifled home into the top-right corner.
The goals continued to flow in east London and another substitute, Morgan, was soon in on the act. Martinez was again involved, slaloming her way down the left before producing a cross that was cleared only as far as the Wales international, who tucked home.
The fourth official held up nine minutes of added time at the end of the second period, and the Hammers only saw time to add to our tally. Substitute Shelina Zadorsky sent a long ball over the top to Asseyi. She took one touch with her chest, set herself and lobbed Stenson with a terrific volley.
After our No20 netted her second, three minutes later, Martinez got hers too, ghosting in at the front post to turn Morgan’s cross into the top-right corner, and cap off a memorable night in east London.
West Ham United: Walsh ©, Endo (Denton HT), Cemal (Zadorsky 82), Nyström (Martinez 60), Hanshaw, Belloumou, Houssein, Csiki, Brasero, Ueki (Asseyi HT), Paví (Morgan 76)
Subs not used: O’Hanlon (GK), Siren, Tysiak, Gorry
Goals: Asseyi 64, 90+1, Martinez 78, 90+4, Morgan 84
Booked: Asseyi
Southampton: Stenson, Mott, Akpan, Goddard, Brazil (McAlonie HT), Ferguson, Edwards (Collett 68), Hack, Primus © (Bashford HT), Watts (Tucker 68), Palmer (Roberts HT)
Subs not used: Prout (GK), Bourne, Peplow, Simpson
Referee: Megan Wilson
Attendance: 546
