Wearing the away kit colours that reflected the blue skies above them, Paul Smyth sent the Northern Ireland faithful into seventh heaven on a sunny spring‑like afternoon in Belfast. Only four minutes after coming on, the 20-year-old Queens Park Rangers winger shook off his South Korean marker just inside the penalty area and fired home the winner on his international debut. He marked it with an acrobatic backwards flip as Windsor Park celebrated.

Smyth’s dream start as a Northern Ireland player also marked an upbeat second coming for Michael O’Neill, who only a few months ago appeared to be taking over at Scotland instead.

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The manager said it should be remembered that Smyth played an under-21s game against Spain only 48 hours earlier. “I Just asked him had he got 10 minutes’ running in him because he played 90 minutes the other night. I told him to go and enjoy it. He’s played on that pitch many times so he’s probably better used to the surface than any of the other players.

“He loved it, you could just see. His enthusiasm for the game is infectious, the boys love him,” O’Neill added.

Smyth’s strike transformed what was heading to be a fair, evenly matched 1-1 draw between the hosts and World Cup-bound South Korea into a friendly victory that should give O’Neill and his squad a major boost.

Initially, though, the South Koreans were a neat, tidy passing unit that appeared about to take Northern Ireland apart. Tottenham’s Son Heung-min created their seventh-minute opener by cleverly lifting the ball into the penalty area for Kwon Chang-hoon to shoot past Trevor Carson.

The home goalkeeper then managed to stop Son himself making it 2-0 soon afterwards when the Motherwell goalkeeper blocked his shot.

A minute later a Jamie Ward effort was ruled out for offside but Northern Ireland did not have to wait too long for an equaliser. In the 20th minute they crafted a clever free-kick about 25 yards out. Ward skipped over the ball but kept running down the right and Oliver Norwood played him in with a low pass for the winger to strike a hard and low cross into the box, which clipped off Kim Min-jae for an own goal.

The quick recovery by O’Neill’s men created a more evenly fought contest up until half-time. But after the interval South Korea enjoyed two spells of sustained pressure. A Lee Jae-sung shot was deflected away for a corner, then Carson got down to his left to save Park Joo-ho’s deflected strike, which could easily have ended up in the net.

Son, who was subject to booing throughout his time on the pitch, then cut in from the left but his shot was blocked by defender Conor McLaughlin.

Shin Tae-yong’s players will have to be far more ruthless and clinical in front of goal when they face Germany, Sweden and Mexico in Group F in Russia this summer, and as with the first half, there was a Northern Ireland revival.

The key substitution came in the 82nd minute when Smyth returned to the pitch where last season his performances on the wing helped Linfield win the Irish Premiership. Now the West Belfast-born player was on an international stage and he latched onto QPR team-mate Conor Washington’s header and showed strength and guile to score the winner with a low drive.

Fittingly it was Smyth who enjoyed the very last kick of the game after he cut in from the wing and forced a save from Kim. The Northern Ireland fans sang “Paul Smyth’s on fire” – the tune they normally belt out in praise of Wigan’s Will Grigg. They have found a new striking hero.