The 21-year-old attacking midfielder has come under scrutiny this season for a string of diving accusations while his form has dipped below that of the last campaign when he scored 22 goals for Tottenham in all competitions.
He failed to start either of England's friendlies against the Netherlands and Italy during the international break but in his 100th Premier League game for Tottenham, he showed exactly what makes him so dangerous.
Christian Eriksen's piledriver had cancelled out Alvaro Morata's opener for Chelsea before Alli, who was quiet in the first half when he was mocked by the home fans, took centre stage in deadly fashion.
In the 62nd minute he showed impeccable timing to beat Chelsea's offside trap and take down England team mate Eric Dier's high through ball with one delicate touch before firing past Willy Caballero with his second.
Four minutes later he showed quick feet to fire home from close range after a goalmouth scramble, sealing his side's first win at Stamford Bridge for 28 years.
It was his first league brace since Tottenham's home win over Chelsea last season and took his season's haul to 12 in all competitions. The result sent his side eight points clear of the Blues in the race for a top-four finish.
