Spoils had been shared in their two previous encounters, with the visitors emerging triumphant in the Barclays Under-18 Premier League South meeting and the home side winning 2-1 in the FA Youth cup tie at St Mary’s last month.

But, with the Youth Cup tie at Everton coming up in midweek, Demkiv’s timely brace handed the youngsters a boost as attentions turn to the game at Goodison Park on Wednesday night.

In search of their first victory at Staplewood since the 4-0 demolition of Fulham back in October, Southampton started with vigour, with frontman Marcus Barnes quick to press the Hammers’ backline.

Firmly in the ascendency in the opening exchanges, Anthony Limbrick’s side almost took an early lead when full-back Niall Mason took aim, but Sam Howes produced a fine stop to turn his effort round the post.

Harley Willard was next to try his luck, but his shot was charged down and cleared. Just minutes later, an inswinging Mason corner warranted a finishing touch, but the cross was nodded clear.

At the other end, West Ham threatened sporadically early on, with their lone forward Jahmal Hector-Ingram keeping skipper Kyle Clinton and Alfie Jones occupied. It was 11-goal Barnes, however, who almost broke the deadlock with 23 minutes on the clock, heading over Willard’s corner.

It took 27 minutes for Upton Park club to register their first shot on target, which came when full-back Alex Pike’s persistence led to a shooting chance for Diangana, but Jake Hallett gathered with ease. Then, a minute later, Pike threaded a pass through for Hector-Ingram, who dragged his effort wide of the far post as the Hammers began to pile on the pressure.

After a high-tempo end to the first 45, in which Demkiv’s teasing centre evaded everyone and Hector-Ingram blazed over from close range, Saints rallied after the break and Barnes’ pace and power almost created a chance for Olufela Olomola, but left-back Vashon Neufville did well to slide in and intercept.

Scully, a persistent threat on the Hammers’ left flank, then looped a speculative volley just wide before Hector-Ingram rounded Hallett, only to be denied by a backtracking Saints defender.

The visitors continued to push hard, with towering centre-half Tunji Akinola nodding a corner wide, but Saints retained a goal threat, even with Barnes having made way with just over 20 minutes remaining. His replacement Carel Kayembe forced a corner but, once again, the killer touch was lacking.

However, with six minutes left on the clock, Demkiv curled home past a helpless Howes from the edge of the area and, three minutes later, wrapped up the victory after pouncing on defensive uncertainty to roll home and give Limbrick’s charges all three points.

Southampton Under-18s: Jake Hallett, Niall Mason, Ben Cull, Joe Lea, Kyle Clinton (c), Alfie Jones, Dan Demkiv, Callum Slattery (Oscar Cvjeticanin 54), Marcus Barnes (Carel Kayembe 68), Olufela Olumola, Harley Willard.

Unused substitutes: Richard Bakary, Will Wood.

Goals: Demkiv (84, 87)

West Ham United Under-18s: Sam Howes, Alex Pike, Vashon Neufville, Mathew Carter, Emmanual Onariase (c), Tunji Akinola, Jeremiah Amoo, Nah Sylvestre (Kieran Bailey 80), Jahmal Hector-Ingram, Grandy Diangana, Anthony Scully (Joe Powell 76).

Unused substitutes: Dan Boness, Jake Eggleton, Idris Kanu.