Chelsea were bidding to become the only English side ever to win 14 successive top-flight matches in a single season but a pair of Alli headers either side of half-time consigned the Blues to a 2-0 defeat and their first league loss since 24 September.
The result means Chelsea miss the chance to move eight points clear at the top of the table while Tottenham climb to third, seven points behind the league leaders.
Chelsea have looked almost unbeatable at times during their relentless winning streak, which has included beating Manchester City, Tottenham in the reverse fixture in November, and Manchester United. But Antonio Conte’s men ran into a Spurs side in supreme form themselves – Mauricio Pochettino, pictured, has now overseen five wins in succession in the league and seven out of their last eight in all competitions.
Central to their resurgence has been the return of key players to both fitness and form, not least Alli, whose third consecutive brace means he now has seven goals in four games, meaning he is back in the same groove that helped drive Tottenham’s surprise title challenge last term.
Chelsea had the first chance of the night and could have taken the lead when Nemanja Matic’s long ball forward found Eden Hazard in space, but the Belgian needlessly rushed into a half-volley and his finish trickled wide.
After another attempted pass drifted astray, Diego Costa sounded off at team-mate Pedro for apparently making the wrong run, which prompted Pedro in turn to berate Costa, all very much to the delight of Tottenham’s fans.
Christian Eriksen drove narrowly wide from distance and Eric Dier’s header at the back post had to be palmed away by Thibaut Courtois – but it was not until stoppage time at the end of the half that the deadlock was broken.
Eriksen and Alli combined, the former lifting a cross to the back post where the latter – who had sneaked between Victor Moses and Cesar Azpilicueta – looped a header perfectly over Courtois.
When Chelsea re-emerged after the break they looked reinvigorated, Costa testing Hugo Lloris with a fizzing shot and then Hazard somehow nodding wide from five yards with the goal at his mercy.
If the visitors had planned an onslaught, however, their momentum was quickly halted as Alli, in a carbon copy of his opener, again eluded Moses and Azpilicueta at the back post and headed in Eriksen’s cross to double the lead.
Chelsea enjoyed a sustained spell of possession after the hour but never really threatened a comeback, despite the introductions of both Willian and Cesc Fabregas off the bench.