Chadli, the Baggies' £13m record buy from Spurs in the summer, rammed in with eight minutes left to put the hosts on the verge of a smash and grab.

But Alli turned in a scrappy leveller and Albion were also indebted to goalkeeper Ben Foster after he stopped Spurs from running riot in the first half.

The England international twice saved from Alli and also denied Erik Lamela, Ben Davies and Christen Eriksen.

Foster needed to be at his acrobatic best with Spurs in complete command from the start as Lamela and Vincent Janssen combined for the former to drag his shot across goal.

Eriksen then fired straight at Foster in the opening 15 minutes as Tottenham probed without exploiting Albion, the hosts planting 10 men behind the ball at all times.

It worked with the visitors restricted to efforts from distance as Davies' drive deflected wide and Eriksen fired off target before they were left frustrated by Foster three times in eight minutes.

The keeper raced out to save at Alli's feet after half an hour and then turned Davies' effort wide as Spurs began to turn the screw.

Alli then acrobatically sliced off target and blew an even better chance after 38 minutes when Foster again came to the Baggies' aid.

Janssen showed good strength to shield the ball and sent Alli racing clear but with just Foster to beat the midfielder's tame effort was beaten away.

And the England international kept the Baggies level again three minutes before half time, turning Eriksen's rasping low strike behind after Albion had been opened up by neat interplay.

Yet, after Foster's heroics the hosts could have gone into the break ahead.

They had been anonymous as an attacking force with Salomon Rondon a lonely sole striker but the Venezuela international almost cashed in when Hugo Lloris spilled James McClean's low shot.

Albion almost made a mockery of Spurs' dominance again two minutes after the re-start but Gareth McAuley failed to get a telling touch on Chadli's corner.

Slowly, the Baggies began to offer more than just their steely first-half resistance and Tottenham's plans were further skewed when Toby Alderweireld was stretchered off following a collision with Rondon and replaced by Eric Dier.

Spurs had failed to find their first-half rhythm and, although Moussa Sissoko's deflected effort dropped just wide after 62 minutes, their level had dropped significantly since half time.

Emboldened, Albion grew into the game and began to unsettle the visitors who had failed to adjust to losing Alderweireld and with eight minutes left they shocked Spurs.

Jan Vertonghen cleared underneath his own bar and from the resulting corner Lloris turned McClean's shot onto the post and Chadli slammed his fourth goal of the season into the roof of the net.

But Alli finally beat Foster with a minute left when Eriksen's shot deflected into his path and he stabbed in from 10 yards.

Eriksen also almost won it in stoppage time when Foster turned his deep free-kick over.