Tottenham Hotspur's chronic inability to convert leads into Premier League points returned with a vengeance in a 2-1 home defeat by West Ham United as their winless run extended to five matches.
West Ham were outplayed in the opening half on Thursday, in which Cristian Romero marked his return from suspension to head Tottenham into an early lead but goals by Jarrod Bowen and James Ward-Prowse turned the derby on its head in the second half.
Bowen equalised after 52 minutes when a rebound fell into his path before Ward-Prowse netted a bizarre winner in the 74th minute following a mistake by Destiny Udogie.
West Ham, now unbeaten in six games in all competitions, soaked up some late Tottenham pressure and held on for a victory that moved them within three points of their London rivals.
While Tottenham remain in fifth place with 27 points they have not won since October and the optimism of their best start after 10 games since 1960 is fading fast.
Tottenham are now the first team in Premier League history to lead 1-0 in five successive games without winning any of them and have taken only one point from the last 15 on offer.
And just as against Chelsea, Wolverhampton Wanderers and Aston Villa they only had themselves to blame.
"We dominated another game of football and didn't turn that into something more tangible and we kept the opposition in the game," manager Ange Postecoglou told reporters.
"I thought we were poor in both boxes today. At halftime 1-0 was not a good performance by us, a good performance would have been 3-0 or 4-0, with the game put to bed.
"When you don't, you get what you deserve."
West Ham manager David Moyes said he was happy his side had trailed only 1-0 at halftime.
"I don't know if we touched the ball for eight or nine minutes," he said. "But we are a team who can give some of the good teams a bloody nose, we have that in us."
For all the praise of Tottenham's free-flowing style since Postecoglou took charge they desperately needed a victory to get their stuttering league campaign back on track.
They had an incredible 92 per cent possession in the opening 10 minutes and duly made it 1-0.
It was Romero's red card a month ago against Chelsea which precipitated Tottenham's slump but the Argentine began to make amends as he met Pedro Porro's corner with a header that arced away from Lukasz Fabianski and nestled in the net.
With West Ham strangely passive, Tottenham should have underlined their superiority but they were over-elaborate at times although Fabianski was required to make sharp saves to keep out shots by Giovani Lo Celso and Brennan Johnson.
West Ham's Lucas Paqueta headed horribly wide when he should have equalised just before halftime and it was a warning that Tottenham failed to heed.
Seven minutes after the break a Mohammed Kudus shot took a double deflection off Spurs defenders Romero and Ben Davies and fell to Bowen who lashed a shot high past Guglielmo Vicario to become only the third Premier League player to score in seven consecutive away games.
Tottenham's fans suddenly had a nagging sense of deja vu and their team self-destructed as Udogie's casual back pass put keeper Vicario in trouble and although he blocked Bowen's initial effort the ball bounced to Ward-Prowse.
His first effort at an open goal hit the post but it rebounded back to him and he made no mistake at the second time of asking to send West Ham's fans into delirium.