Dele Alli was on target and Harry Kane narrowed the gap in the Premier League's golden boot race as Tottenham strengthened their grip on a Champions League qualification place with a 2-0 win over Watford. Spurs went into Monday's game at Wembley just two points ahead of Chelsea, who are on a run of three successive league wins and seeking to keep the pressure on their cross-city rivals in the race for the final spot in Europe's top club competition. But Tottenham extended that gap to five points with just three games to play thanks to an ultimately routine win against a Watford side still not quite safe from relegation. A goalkeeping error from Orestis Karnezis enabled Dele Alli to open the scoring 16 minutes in with his fourth goal in five Premier League appearances. Tottenham have not lost in the top flight this season when opening the scoring and, though captain Hugo Lloris was required to maintain their advantage, Kane gave Watford a mountain to climb with his 48th-minute effort, moving him onto 27 league goals - four behind Liverpool's Mohamed Salah. Mauricio Pochettino's men were in control from then on, with a seemingly minor injury that forced Mousa Dembele off the only blot on the victory as Watford remain six points above third-bottom Southampton, who have a game in hand. @HKane not giving up on that Golden Boot #TOTWAT pic.twitter.com/bA6iYAcoVb — Premier League (@premierleague) April 30, 2018 Eric Dier threatened early for Tottenham as he headed over a Dembele cross but they were largely unconvincing until Karnezis gifted them an opener. Kieran Trippier whipped in a cross from the right and Karnezis fumbled what should have been a straightforward take, allowing Christian Eriksen to lay the ball off for Alli to calmly slot home. 10 - Christian Eriksen (10 goals, 10 assists) is the third Tottenham player to hit double figures for both goals and assists in a single Premier League season, after Jurgen Klinsmann in 94/95 and Emmanuel Adebayor in 11/12. Star. pic.twitter.com/PyRsaxCFId — OptaJoe (@OptaJoe) April 30, 2018 Watford would have levelled if not for a smart save from Lloris, who denied Andre Gray from close range after Etienne Capoue had intercepted and played the forward in on goal. Spurs had a penalty claim waved away by referee Michael Oliver when Abdoulaye Doucoure appeared to bundle over Son Heung-min in the area but they were fortunate to go into the interval level. Richarlison raced clear for Watford only to be thwarted by Lloris, who got down low to his left to preserve parity before racing way off his line to dispossess Doucoure and quell another dangerous attack from the visitors. Watford's inability to beat Lloris was swiftly punished three minutes after the restart as Kane doubled Spurs' lead. The England striker initially slipped as he overran Son's low cross, but the ball rolled through to Trippier and Kane was alert to pick himself up and tap in the right-back's subsequent delivery. Kane was presented with a simple chance to score his second but mis-kicked with the goal gaping after Jan Vertonghen clattered the post with a header. Watford's best opportunity to get back into the game came when Troy Deeney nodded down for Richarlison, who could only fire way over on a frustrating night for Javi Gracia's side but an important one for Tottenham in their pursuit of a top-four finish.