In the final minute of Chelsea's clash against Tottenham last season at Stamford Bridge, Harry Kane scored an equaliser that should not have stood.
That was because, at the preceding corner, Cristian Romero yanked Marc Cucurella down by the hair - an incident that VAR should have cleared up.
Dean was the VAR that day, which has since been remembered for its fiery conclusion between Antonio Conte and Thomas Tuchel.
And he admitted to Simon Jordan on his podcast Up Front that he did not intervene as he did not want to give any more grief to his 'mate' Anthony Taylor, who was refereeing at the time.
"I missed the stupid hair pull at Chelsea versus Tottenham which was pathetic from my point of view," Dean told Jordan.
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"It's one of them where if I had my time again, what would I do? I'd send Anthony [Taylor] to the screen.
"I think I knew if I did send him to the screen… he's cautioned both managers, he's had a hell of a game, it's been such a tough game end to end.
"I said to Anthony afterwards: 'I just didn't want to send you to the screen after what has gone on in the game'.
"I didn't want to send him up because he is a mate as well as a referee and I think I didn't want to send him up because I didn't want any more grief than he already had.
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"Anthony, he is big and bald and ugly enough to know if he is going to the screen he is going to the screen for a reason.
"If someone pulls their hair now it's dead easy. It's just a brainwave by me, a really bad call by me, and it kind of affected me as VAR going forward."
Kane's goal came in the 96th minute from the corner after Romero pulled Cucurella to the ground by his hair, after Edouard Mendy tipped a goal-bound header over the bar.
VAR did not intervene despite protests from Chelsea players and Spurs took the second corner, which Kane scored to make it 2-2.
Conte and Tuchel would go on to both get sent off after clashing at full-time after simmering tensions throughout the game.
Dean only operated VAR last season after standing down as a referee on the field but was kept out of Stockley Park, where the VAR hub is situated, for two months after the incident.
He later retired from refereeing altogether at the end of the season and has since taken a role as a refereeing analyst on Sky Sports.