Tottenham, the first team to not sign anyone since the summer transfer window was in 2003, put that chatter to rest -- at least temporarily -- with the victory against a club whose manager publicly bemoaned a lack of additions.
Spurs opened the scoring in the eighth minute when Cristian Eriksen sent his corner into the mixer, Davinson Sanchez fired toward the far post and Vertonghen scored from a header just in front of Paul Dummett.
The Goal Decision System showed the header crossed the goal line by 9mm, with 5mm considered the technology's margin for error.
Newcastle answered three minutes later, with Joselu meeting a cross from Matt Ritchie at the edge of the box and glancing a header past the helpless Hugo Lloris.
But Spurs would not be denied, with Alli coming through to restore their lead. Serge Aurier found his late-running teammate with a long cross from the right into the box that Alli tucked in after breaking past DeAndre Yedlin.
Newcastle had two opportunities to equalise after half-time, but Mohamed Diame struck the left post from close range in the 47th minute and Kenedy, running free on the left four minutes later, wasted too much time before being snuffed out by Spurs' defence.
And Salomon Rondon, who came on as a sub for his first appearance since finalising a loan from West Bromwich Albion, hit the crossbar in the 85th minute after his shot was deflected by Vertonghen.
Yedlin was helped off the pitch in added time and television cameras showed him being helped slowly through the tunnel by a member of Newcastle's medical staff.
Harry Kane, who last season became the first Tottenham player to score 30 goals in a Premier League campaign, stretched his run to 14 games for Spurs in August without a league goal.
Tottenham handed Luke Amos his first Premier League appearance when he was subbed on for Eric Dier in the 89th minute.