The midfielder scored twice as Spurs outclassed the defending champions and booked themselves a spot in the round of 16 for the first time in seven years. The north Londoners had proved their credentials two weeks ago when they emerged from the Santiago Bernabeu with a creditable draw, but their performance at Wembley was one of the club's great European nights.
Yet Alli said the result was far from surprising. "It was a fantastic display by us," he was quoted as saying by the Mirror. "We knew if we stuck to our game plan and were solid at back then we'd get chances. We're very happy. I wasn't surprised we were dominant."
Christian Eriksen, who scored Spurs' third goal of the evening to cap a brilliant counter-attack and condemn Real to their first group stage defeat for 30 games, also praised his side's approach to the game.
"We played a professional game," he added. "If we had more composure we could have got more. We take this on to the next stage. We're happy to be through."
Following a dismal Champions League campaign last season, when they won just two of their games and dropped into the Europa League, Spurs are unbeaten in Europe this season and lead Group H by three points. With a trip to Dortmund to come before a home game against Apoel Nicosia, Mauricio Pochettino's men are well placed to win the group, which would in theory earn them an easier draw for the round of 16.
And, Alli, who made his return from a three-game European ban against Real, insisted the result proved Spurs can go toe-to-toe with Europe's elite.
"We don't want to just compete with these teams, we want to beat them," he added. "I'm happy to get two goals but more importantly it was a win."
Spurs looked to have been handed the toughest draw out of all of the English clubs when they paired in the same group with 12-time winners Real and Dortmund but have made surprisingly easy work of qualification.
The result was particularly pleasing for Pochettino, particularly as it came after his side were knocked out from the Carabao Cup by West Ham United and lost to Manchester United in the Premier League.
The Argentinian refused to get carried away following his side's performance, but admitted Spurs can start to dream of bigger things in the future.
"Victories are important for us and the players and for the fans because it is Real Madrid and they are the best team in the world," he told BT Sport. "It is fantastic to feel that you can compete but it is a long way to the end of the season. we must achieve our target and challenge. We showed it today and must do it again on Sunday.
"It gives great belief to everyone, great confidence. That is so important now. We are into the next stage of the Champions League. It is important that we are two games ahead. But now it is important to be ready to compete against Crystal Palace. But we must move on."