It happened after an FA Cup match against Norwich City, which Spurs eventually lost on penalties.
When the final whistle blew, Dier leaped over the pitch-side barriers into the stands, heading straight for a fan who had been sitting in the top row of seats in front of the clubs hospitality boxes. The 26-year-old was incensed because the fan in question had been allegedly insulting his brother, who was sat watching the match nearby.
Dier was restrained by fans and security officials, whilst the supporter in question was escorted out of the ground.
The matter was reported to the local police, but, after an investigation, they decided to take noa action.
However, the Football Association (FA) has not been so lenient in announcing the outcome of their own disciplinary findings, which had been delayed because of the Covid-19 outbreak in the UK.
They have judged that his actions constituted threatening behaviour, and that his conduct had been improper.
Not only have they given the defender a four-match ban, but they have also warned him about his future conduct.
In part their decision was justified by what happened in the aftermath of the incident, with pushing and shoving in the stands, and a melee developing around one of the exits. It was also felt that he had such a poor example, and that he was a high profile figure whose actions would be followed by many.
The player has always argued that his actions were designed solely to protect his brother, but the disciplinary panel has disagreed with that interpretation of events.
Spurs are unlikely to appeal the ban because they fear a further punishment if that proves to be unsuccessful.
This is by no means the first time a professional footballer has got into trouble for attacking a fan, with probably the most famous example being Manchester Uniteds Eric Cantona, who was given an eight month ban from the game for attacking a Crystal Palace fan during a match in January 1995.
It rarely ends well for the player or club, and however much the degree of provocation, it is better to turn the other cheek and accept it.
It is perhaps one small consolation for the fact that games are now being played behind closed doors there are no spectators present to insult players or their families!