LONDON (AFP) - Michail Antonio ruined Mauricio Pochettino's birthday as the West Ham winger sealed a 1-0 win that stopped Tottenham taking over at the top of the Premier League on Wednesday.
Pochettino hoped to celebrate his 44th birthday by masterminding the victory that would put his club in pole position in the English top-flight for the first time since August 2009.
But Antonio struck early in the first half at Upton Park and Tottenham were unable to respond as they suffered an untimely first defeat in seven league games.
Leicester's draw against West Bromwich Albion on Tuesday had paved the way for second placed Tottenham to seize the initiative as they chase a first league title since 1961.
However, the last time Tottenham were top in March was way back in 1964 and they couldn't end that sequence following a tame display that left them three points behind Leicester ahead of Saturday's north London derby against third placed Arsenal, whose loss against Swansea on Wednesday was the only bright spot for Pochettino.
West Ham's victory kept them in the hunt for a top four finish as they try to mark their final season at Upton Park by securing an unexpected Champions League place.
Pochettino made four changes from the team that came from behind to defeat Swansea on Sunday, with Kieran Trippier, Ben Davies, Ryan Mason and Nacer Chadli selected in a bid to keep his side fresh.
But the changes did little to aid Spurs, who may also have underestimated the level of motivation in a West Ham side fired up by their vociferous fans to upstage their hated London rivals.
Whatever the cause, Slaven Bilic's side made a blistering start and stunned the lacklustre visitors with a goal in the seventh minute.
From Pochettino's point of view it was a disappointing one to concede as a corner reached Antonio, who had easily escaped Chadli's attempt to mark him, and the winger had time and space to bury his header past a weak attempted save from Hugo Lloris.
Lloris partially redeemed himself when he sprang across goal to keep out Mark Noble's powerful long-range effort.
Pochettino's men had thrashed the Hammers 4-1 in November, but the hosts were unbeaten at home since August and it was easy to see why as their relentless pressing rendered Tottenham toothless in attack.
Standing arm crossed with a furrowed brow on the touchline as rain lashed down, Pochettino was hardly having the best of birthdays and there was little sign of his players, who failed to muster a shot on target in the opening 30 minutes, lifting his mood.
As he has so often this season, Dimitri Payet was at the heart of all West Ham's best moves and he brought Lloris into action at the end of another incisive raid.
Pochettino's team finally showed signs of recapturing their recent swaggering form in the second half and Erik Lamela threatened when he headed wide from Trippier's cross.
The key moment came when Toby Alderweireld's long-range strike was parried by West Ham goalkeeper Adrian into the path of Harry Kane, but the England forward, usually so lethal in front of goal, made a complete hash of his effort.
Tottenham defender Kevin Wimmer, already on a booking, might have feared a red card after tripping Emmanuel Emenike, but referee Andre Marriner instead gave a foul against the Hammers striker.
Pochettino sent on Dele Alli and Son Heung-min in the closing stages, yet the birthday boy's party was destined to end up a damp squib as Spurs ran out of steam.