At the end of a hugely satisfying night for Tottenham Son Heung-min walked off the pitch with his shirt untucked, the ball at his feet and a look of boyish joy on his face. He was doing keepie-ups, still wanting to entertain the crowd after another of those occasions when it can be difficult to remember Spurs did not sign anyone in the last transfer window, or the one before that, are not even playing in what they can genuinely call a home stadium and have Harry Kane and Dele Alli among their absentees.

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Once again Mauricio Pochettino’s players showed their qualities of togetherness, resilience and, at times, great skill. They keep doing it, rising to the challenge, absolutely determined to show they can outdo teams with bigger reputations in the Champions League and more experience of European football at its highest level. Son was their first scorer and his hard running and intelligent forward play set the tone. Jan Vertonghen, a revelation in his left wing-back role, was next and, finally, it was the substitute Fernando Llorente heading in a corner to put Spurs in a position of command.

The last two goals came in the 83rd and 86th minutes, turning a narrow lead into a resounding one, and a side who had barely scraped through the group stage are now one solid display away from reaching the quarter-finals. Spurs had dominated against the team who, to recap, are holding off Bayern Munich, the Bundesliga champions in each of the last six years, at the top of the German league. Pochettino talked about it being one of the great occasions from the last two seasons as tenants at Wembley and, from here, it would need a spectacular collapse if his team are unable to finish the job at the Signal Iduna Park on 5 March. One goal for Spurs would mean Dortmund need five.

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No wonder Son was grinning. He, more than anyone, took the fight to Dortmund, with his ability to create danger, his licence to roam and apparent immunity to fatigue. Son was playing, officially, as a centre-forward, but one who drifted to both sides or even dropped back into his own half to collect the ball. He was four roles in one. It made him an elusive player to mark and it was his goal, early in the second half, that dramatically changed the complexion of the match.

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Until that point Dortmund had been marginally the better side, quick to the ball, strong in the tackle, with the kind of self-assurance that comes from being five points clear in the Bundesliga. Hugo Lloris, the Spurs goalkeeper, was far too busy for Pochettino’s liking in the first half. Jadon Sancho, being watched by Gareth Southgate, was prominently involved and Dortmund’s confidence during that period could probably be summed up by Achraf Hakimi, their right-back, venturing forward to slip the ball through Vertonghen’s legs for a perfectly executed nutmeg.

That all changed in the 47th minute when Hakimi tried the same again, except this time he was inside his own half with other players crowding him out. Spurs retrieved the ball and, when Vertonghen looked up, he could see Son signalling for the ball inside the penalty area. Vertonghen was playing in an unorthodox role and many Spurs fans might have felt unsettled to see the centre-half being asked to tread a path up and down the left wing. They need not have worried: Vertonghen’s performance was one of the great triumphs of Pochettino’s team selection. His cross was expertly delivered and Son’s volley flew into the net.

Facebook Twitter Pinterest Fernando Llorente celebrates with his teammates after scoring the third Spurs goal. Photograph: Tom Jenkins/The Guardian

The most surprising part of Dortmund’s deterioration was how long it took for the players in yellow to shake their heads clear from that opening goal – if they ever did. Sancho faded badly but, to give him his due, he was not alone. In addition Spurs looked far more assured for the remainder of the game, attacking with real purpose and defending much more stoutly than earlier in the match when Juan Foyth committed the centre-half’s sin of losing the ball inside his own penalty area, leaving Christian Pulisic with the chance to left fly with a left-foot shot.

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Once they had taken the lead, the dilemma for Spurs was how much they should press forward in the hunt for more goals if that opened up the possibility of leaving themselves vulnerable to the counterattack. As it was, they got the balance just right. They must have also been encouraged by what was becoming increasingly obvious, namely that Dortmund were faltering. Son, in particular, played as though he would not be entirely satisfied with only a one-goal lead. His attitude was infectious and, once Vertonghen had the better of Sancho, the Spurs player was emboldened to go forward more.

Perhaps Spurs had also been encouraged by the reports from Dortmund’s previous two games, when Lucien Favre’s team had conceded three in each of their assignments against Hoffenheim and Werder Bremen. Vertonghen’s goal was a side-footed finish, unchallenged, after Dávinson Sánchez won the ball back and Serge Aurier picked out his run with an excellent cross from the right.

The marking was poor, to say the least, and it was the same again three minutes later when Spurs won a corner on the left. Christian Eriksen swung the ball into the penalty area and Llorente, who had been on the pitch only two minutes, applied the decisive header.