West Ham's Manuel Lanzini struck to leave Tottenham's Premier League title hopes in tatters and Chelsea with one hand on the trophy.
Chelsea's grip on the Premier League title strengthened after West Ham battled to a shock 1-0 win over second-placed Tottenham.
Mauricio Pochettino's side headed into the match on a superb run of nine consecutive victories that had prevented Chelsea from turning their bid for glory into a procession.
But they were short of their best at the London Stadium and Manuel Lanzini's goal 20 minutes into the second period ensured Spurs would remain four points behind Chelsea, having played a game more.