At the age of just 17, Alli burst onto the scene with MK Dons and was extensively scouted by a number of Premier League clubs.
Eventually, his calls were answered and an initial £4million fee was agreed and United’s media team were briefed to prepare for the signing to be completed.
Discussions over a contract offer held up the deal and allowed Spurs to make a last-ditch - but ultimately successful - move for his services.
Alli went on to enjoy a productive career with the North London club and won the first of 37 England caps within months of his move to White Hart Lane.
However, his progress has stalled recently and the midfielder has made four Premier League appearances since October.
That has led to speculation he will be allowed to leave Spurs this month - and Newcastle are one of a number of clubs believed to be interested in taking the 25-year-old on loan for the rest of the season.
Dele Alli on failed Newcastle move in 2015
Speaking to Sky Sports last season, Alli said: “There were a few different reasons. Obviously, from the family point of view, there were clubs interested from up north.
“Liverpool were at the time, but I don’t know how serious they were, but I remember Newcastle was quite a big one at the time.
“But from a family point of view, I was going up there by myself, and they were a bit worried about me being up there by myself so far away, it’s not local to them.
“In the end, the decision was mine, but I don’t know what happened, the deal didn’t go through anyway, and I don’t think they wanted me in the end!
“That was a bit before Tottenham.
“When you’re still young, it’s hard to see the bigger picture, and when it happened at first, I was sort of really angry, it felt like people were stopping me from leaving! But I know that wasn’t the case.”
‘Newcastle have unbelievable fans’, says Alli
Alli has scored two goals in four appearances against the Magpies - and both of those strikes have come at St James Park.
The midfielder scored his side’s first goal as Spurs earned a 2-0 win on Tyneside on the opening day of the 2017/18 and followed that up with the decisive strike in a 2-1 win on the first fixture of the following campaign.
Alli reflected on the second of those meeting and hailed the St James Park faithful as “unbelievable fans” in a post-match interview with the broadcaster.
“It was very tough,” he explained.
“Newcastle is a difficult place to come.
“Newcastle have got unbelievable fans, it is an atmosphere that is not too nice to play in but we knew the job we had to do.”
Whether or not he gets to experience that atmosphere in a black and white shirt remains to be seen.