It has not always been the way in the past few months but it was hard to wipe the smile off the face of Aiyawatt ‘Top’ Srivaddhanaprabha, the ­Leicester chairman, as Abdul Fatawu completed his hat-trick, capping the scoring in a rout of Southampton on a night that left an instant return to the Premier League seemingly all but a formality.

After the heavy financial losses, the legal action against the English Football League after being placed under a transfer embargo, the angst among supporters and the surrender of what looked an unassailable lead at the summit – they were 17 points clear of now second-placed Leeds at the beginning of the year – the prize of promotion is finally in plain sight.

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Enzo Maresca shot off down the touchline, arms outstretched after Jamie Vardy scored the fourth and then came the inevitable chants from the home support. “We are going up,” they sang. The olés were out in full force and Southampton, who played like a team resigned to the playoffs, well beaten.

Russell Martin bemoaned the way his side capitulated after Wilfred Ndidi headed in Leicester’s second goal on 62 minutes, after which a delighted Top banged the ­advertising hoardings below the directors’ box in delight.

“It is not my job to make them feel good about tonight,” the ­Southampton manager said. “They need to feel some pain, the same pain I’m feeling right now. It is pathetic it ends up 5-0.

“It is their job as a group to rally around each other. The team that plays from now on in will be the team that really fights for their teammates, really wants to win.”

Leicester, on course to reach the 100-point mark, could be promoted without kicking another ball, though that would require QPR to beat Leeds at home on Friday. They are now five points clear of third-placed Ipswich, four of Leeds and their ­supporters could be forgiven for planning a ­promotion party at Preston on Saturday. By the time Leicester host Blackburn on the final day, a top-flight return could be wrapped up.

“In this moment we know the most important thing is to win one more game,” Maresca said.

Leicester were unconvincing in victory against West Brom on Saturday, but once Southampton raised the white flag they confidently dissected their opponents here. Fatawu’s second was the best of the lot, a peach that curled into the top corner to make it 3-0 and he finished the night with the match ball in his grasp.

He slotted in the first after ­nipping behind Kyle Walker-Peters to latch on to a Kiernan Dewsbury-Hall through ball but Ndidi’s header from Stephy Mavididi’s cross felt significant.

Vardy got in on the act with a first‑time finish before Fatawu added a fifth, at which point the Leicester fans called for a sixth.

Fatawu, on loan from Sporting, was excellent, though Maresca wants him to retain focus. “I just said to him: ‘The next game you will be on the bench,’” the Leicester manager said, smiling.

Leicester, even with only a one-goal buffer, were in cruise control. Mads Hermansen dropped a ­simple, ­hanging David Brooks cross but that was probably because he was rusty from having nothing else to do. Moments before Ndidi beat Ryan Manning to the ball in the area to head in the second goal, a ­speculative Che Adams effort summed up ­Southampton’s night.

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A yard or two inside his own half, the striker resorted to trying to lob ­Hermansen but his shot was undercooked and barely made the penalty area. Two minutes later, the hosts doubled their advantage and the game felt as good as done. Then they turned on the style.

“To get the win Saturday and put that performance in, everyone’s over the moon,” Vardy said.

This game was a slow-burner compared to when these sides met in September, when Vardy scored inside 21 seconds en route to a 4-1 victory at St Mary’s. It was then that Leicester announced themselves as the ­division’s pacesetters and, after an alarming wobble, they are almost over the line. Southampton, meanwhile, have lost their past two matches and must rouse themselves for the playoffs.

On this evidence, Martin has a job on his hands. “I did not like what I saw from our team at 2-0 down, our body language, throwing arms up in the air,” he said. “I did not like that one bit and it has surprised me. The fans deserve better than that.”