Ange Postecoglou wore the thousand-yard stare. The game had felt over at half-time, his Tottenham team two goals to the good, their control almost total, en route surely to a sixth straight win in all competitions.

Now the head coach stood motionless on the touchline, hands buried deep into coat pockets, struggling to process what had happened. Which was an astonishing Brighton comeback, one that involved them bouncing up from the canvas and surging into the lead just after the hour. They would not relinquish it, the home support celebrating wildly at full-time.

There was an uncomfortable spotlight on the Spurs defending, with Destiny Udogie enduring a personal nightmare, culpable to varying degrees on all three goals. Yet he was not alone. Micky van de Ven, for example, will not enjoy the inquest into his role on the first two goals, which were scored by Yankuba Minteh and Georginio Rutter. Ditto Rodrigo Bentancur on what proved to be the winner, which was headed home by Danny Welbeck.

More broadly, as Postecoglou would make clear in searing style, this was an abdication of responsibility from his players; their failure to do the very basics – beginning with carrying some kind of fight – cutting him to the core. He has not been this frustrated after a game, this outspoken about the shortcomings of his team.

Credit to Fabian Hürzeler, the Brighton head coach, who made a key substitution at the interval, replacing Ferdi Kadioglu, who endured a torrid time at left-back, with Pervis Estupiñán. And to every player in the blue and white. They refused to believe that defeat was their destiny, even if they surely could not have envisaged the extent of the Spurs capitulation.

Brighton located the necessary levels of intensity, of ruthlessness, with Kaoru Mitoma the spark; a blur of quick feet and direct movement. He was virtually unplayable.

Earlier in the year, when Hürzeler was in charge at St Pauli, Postecoglou had invited him into Spurs to share some of his knowledge. “If someone knocks on your door and wants a cuppa, let them in your house,” Postecoglou said. “He’s not going to take your furniture or steal your cutlery.” Here, Hürzeler plundered extensively, Brighton jumping above Spurs and up into sixth place in the table. Their £150m summer squad rebuild has its latest dividend.

It was almost impossible to reconcile the first-half performance with what followed from a Spurs point of view. Their start had been blistering and the story looked set to be about a sixth goal in as many games for Brennan Johnson, about James Maddison making light of his continued omission from the England squad with another influential display. Dejan Kulusevski revelled in his inside forward role, surging up and down; more up than down.

Spurs pressed high and aggressively, forcing turnovers in dangerous areas. Timo Werner’s pace was too much for Joël Veltman, even if his end product was typically frustrating. Dominic Solanke impressed.

Maddison had a goal ruled out by the VAR, who spotted that Pedro Porro was offside before he crossed, and the breakthrough was all about Spurs’ hustle, Udogie and Maddison combining to rob Rutter. From there, it was Solanke to Johnson and Johnson with the low first-time finish. The biggest compliment to pay the in-form winger was that the outcome was never in doubt.

Spurs had created a clutch of decent openings in the first 10 minutes alone, Kulusevski and Maddison central to everything, and when the former sent Johnson through in the 43rd minute after a neat Solanke lay-off, a Brighton fan next to the press box summed things up. “It’s too easy,” he yelled. Johnson banged the shot over the crossbar.

By then it was 2-0, the goal a handling disaster for Bart Verbruggen. Solanke led the break and when Werner pulled back, Maddison took a touch and side-footed for the bottom corner. Verbruggen allowed the ball to squirm underneath him.

Brighton, who lost Adam Webster to a muscle injury in the early running, barely contributed to the first half, save for a couple of Welbeck moments. He prodded wide from a Mitoma cross when he ought to have done better and flashed a header wide. The second-half turnaround was remarkable.

Hürzeler’s introduction of Estupiñán revived his team on the left, with Mitoma coming alive. By the 58th minute the winger had set up two goals and the game was level. Van de Ven and Udogie each miskicked before Minteh spun to score and the Spurs pair were brushed aside on the equaliser, with Rutter swerving away from them and picking out the bottom corner.

There was an element of inevitability about the Brighton goal for 3-2, Spurs all at sea, Udogie yet again at fault. Rutter got around him too easily but Bentancur had moved across to deal with the forward as the ball ran along the byline. Except he did not. Rutter slid for it, showing the desire, and his tackle became the perfect cross, Welbeck rising to nod past Guglielmo Vicario.

Spurs disappeared without trace. Their only real chance for the equaliser came when Udogie cut inside and unloaded a low shot. Verbruggen got down to his right to save.