It is the time of the season when the nerve ends are raw and the focus turns inwards. Tottenham knew what they needed to do here. There was not a single soul connected to the club who considered this fixture as anything other than must-win. The season's final weeks will surely bring twists but it did not matter. Southampton had to be vanquished.
Thanks to Gareth Bale, who appears to be on a one-man mission to drag Tottenham into the Champions League, they got the job done. The performance was sluggish and disjointed and, by any reckoning, Southampton did not deserve to lose. They ought to have led at the interval and they were comfortable for most of the second half.
But Tottenham have Bale and, yet again, he found a way to be decisive.
He had been moved about by Andre Villas-Boas, from the centre to the left and then the right and, frankly, he had been anonymous for 85 minutes. But he received possession on the right, surged inside and away from Luke Shaw before blasting a low, left-foot drive past Artur Boruc.
It was his 20th league goal of the season and he became the first Spur to reach the mark since Jurgen Klinsmann in 1994-95. This was his 200th game in Tottenham colours and his dramatic cameo brought Southampton, the club where he emerged through the academy, to their knees. Tottenham will now look ahead to Wednesday's visit to Chelsea with optimism.
Tottenham had not won a Saturday 3.0 league game here all season so there were no tears when the kick-off was delayed by 30 minutes due to the chemical spillage on the M25. Spurs started slowly, as they have often done, and it was Southampton who were more polished and threatening.
The visitors had two wonderful chances in the first half. Rickie Lambert created the first for Nathaniel Clyne on 10 minutes, when he dropped a pass over Tottenham's backline. It was remarkable to see how much space the marauding full-back was afforded and when the ball sat up for him and begged to be thumped home, there was palpable apprehension around the stadium. Clyne's sights were awry.
Southampton also cursed when Lambert's low 35th-minute free-kick was tipped on to the post by Hugo Lloris. From the rebound, Guly do Prado dug out a cross only for the onrushing Steven Davis to plant his header straight at the Tottenham goalkeeper.
The visitors were compact and composed, whereas Tottenham laboured. When Mousa Dembele limped off in the 34th minute, the home team was further disrupted. They created nothing in the first half, with Bale well marshalled. Villas-Boas grasped for solutions.
He moved Bale to the left at the start of the second-half and pressed Clint Dempsey up alongside Jermain Defoe and he then switched Dempsey to the right to accommodate the introduction of Emmanuel Adebayor. Yet it was the players in red that bristled with assurance. Adam Lallana's quick feet were a delight and, after outfoxing Michael Dawson, he was let down by a tame finish.
The anxiety levels rose within the home crowd, who wondered where the inspiration might come from or, at the very least, how Jack Cork and Davis might be knocked from their stride in the Southampton midfield.
Tottenham flickered on 68 minutes when Adebayor touched Tom Huddlestone's ball down for Dempsey but the American's first touch was poor and his second saw him bundle the ball over the bar.
Villas-Boas hauled him off, bringing on Glyfi Sigurdsson on the left and moving Bale over to the right.
There was desperation in the closing stages. Jan Vertonghen nearly bundled home after a flap from Boruc and Bale appealed in vain for a penalty after a hack from Cork. Southampton felt that they were poised to reach the 40-point mark but Bale had other ideas.