Southampton’s squad ventured to the Isle of Wight for a get-together at the end of the regular season, where the majority owner, Dragan Solak, who dragged his fingernails down his face during the final minutes at Wembley, promised they would have the party of their lives if they sealed promotion.

The chances are those celebrations will take place somewhere more salubrious after Adam Armstrong’s goal secured Southampton a return to the Premier League at the first attempt, via a typically fraught Championship playoff final.

For Leeds it was more playoff final agony, this being their fourth to end in tears. For Russell Martin, a ­beautiful ending to a marathon season but for Daniel Farke, under whom he played at Norwich, it was an altogether different feeling in the pit of the stomach.

As this game ticked towards the 103rd minute, Armstrong prematurely whipped off his shirt before quickly wrestling it back over his GPS vest after he realised his mistake. He was able to laugh about it seconds later, when this time the referee blew his whistle not for a foul against Joe Aribo but to signal full-time, con­firming Southampton’s victory.

His overexuberance was more than understandable given his clinical first-half strike was the difference in this encounter. Leeds never really recovered, though Daniel James smacked the underside of the crossbar towards the end of normal time and then forced Alex McCarthy, who had been third‑choice goalkeeper for much of the season, into a fine save down to his left. ­McCarthy had gone shopping in London on the day of his first league start of the season but then Gavin Bazunu ruptured his achilles in the warmup against Preston and McCarthy returned to action. “I guess I’m a bit of an idiot for not playing him sooner,” Martin said afterwards.

The Leeds squad waited on the pitch, many applauding, to witness Southamp­ton’s players pass the winners’ trophy between themselves in the royal box. The minority owner, Katharina Liebherr, whose father, Markus, died a year after buying the club in League One in 2009, was among those to embrace the players. Martin stayed on the pitch, hugging his backroom staff before enjoying a moment to himself as the music blared over the speakers. By that point a red haze had fallen over the stadium. Jack Stephens, the captain, struggled to hold back the tears.

The goal embodied everything about Southampton’s style, the ultimate vindication for Martin’s methodical approach.

It was a sequence that took Glen Kamara and Georginio Rutter out of the game, a three-pass move that pulled Leeds apart, destroying any semblance of structure. Seconds before Taylor Harwood-Bellis assumed possession inside his own half, Martin pleaded with his players to remain patient: pick your moment. Then came the killer pass, first from Flynn Downes to feed Will Smallbone, who joined Saints as an eight-year-old and was not short of familiar faces in the home support.

The Leeds captain, Ethan Ampadu, was guilty of getting sucked towards the ball and Smallbone poked a pass into Armstrong, always a willing runner, who galloped into the gaping hole in the centre of the opposition defence. It was a case of role-reversal; Armstrong, who earlier declined to shoot in favour of cutting the ball back for Smallbone, found the far corner with all the panache of a player scoring his 24th goal of the season.

“We missed a few passes that we would never normally miss so I was just trying to tell them to stick to the gameplan,” Martin said. “We had one brilliant action where Arma [Armstrong] went through and tried to square it to Will and I felt that put a little bit more fear into Leeds to press more aggressively. We scored a really, really nice goal; it was something the guys work on a lot with the way we built up. I didn’t want us to defend as long as we did in the last 25 minutes but with the tension in the game I understand that, because it is such a big occasion.”

Leeds’s attacking players wilted when they needed them most. For Southampton, the sight of Wilfried Gnonto and Crysencio Summerville, the division’s player of the season, heading to the away dugout after being withdrawn midway through the second half was the closest thing to a veiled compliment given the stakes.

Archie Gray drilled wide on four minutes but, after the early promise, Southampton assumed ­control and were rarely troubled.

Southampton came close to doubling their advantage approaching first-half stoppage time, when Smallbone located an unmarked Armstrong at a free-kick. Armstrong got the ball under his spell, swivelled and then shot at goal, through the legs of Joël Piroe, forcing Illan Meslier to push his effort clear with his right glove. Joe Rodon hacked the ball to safety to prevent Harwood-Bellis jumping on the rebound. Armstrong then had another effort blocked by Rodon.

There was a reason Martin was intent on signing Downes on loan from West Ham last summer. Downes, whom Martin signed for his previous club, Swansea, was omnipresent, one minute a human vacuum of sorts and next ­breathing life into ­Southampton attacks.

Harwood-Bellis, whose loan move from Manchester City now becomes permanent, was also outstanding. Southampton offered Leeds little encouragement but when they did the substitute James rattled the underside of the crossbar with 84 minutes on the clock. James forced a fine save from McCarthy with a swerving shot deep into second-half stoppage time, but the Saints would not be blown off course late on.