After a first half in which Tottenham were two goals to the good through Moussa Sissoko and Dele Alli even without getting out of first gear, things looked bleak for under-fire Hammers boss Slaven Bilic, who made nine changes from their defeat to Brighton.
The east Londoners, who before Wednesday night had played one and won one at the new Wembley -a play-off final win against Blackpool - came back out after the interval and began to show a desire and intent which was totally absent in the first half.
Manuel Lanzini, upon whom hopes of a turn in form had been placed when coming back from injury, finally began to have the desired impact.
The Argentine, dubbed ‘The Jewel’ during his time at River Plate, sparked for Bilic after the break and, despite not making it onto the scoresheet, proved the most potent attacking threat in claret and blue having been allowed to roam further forward than during the first 45 minutes.
Andre Ayew grabbed two goals, both instinctive finishes, to draw level before Angelo Ogbonna headed home to complete the most unexpected of turnarounds inside 15 minutes.
It is the first time Spurs have let a two-goal lead slip under Mauricio Pochettino, while Bilic is left with a welcome headache for once after a stellar showing from his perceived second string.
