The passengers intervened when the man confronted a woman sat three seats down from him who appeared to be breastfeeding.
He said:"I don't want you to do it in front of me. Could you not express before you came on here?
"I just feel uncomfortable with it, please I'm asking you nicely, please maybe do it on the next carriage.
"Why should she be allowed to expose herself like this?"
A couple sitting opposite the bickering pair told the man that he should be the one to move if he was feeling uncomfortable, not the mother, who they reassured was "doing nothing wrong".
As the mother retaliates, the man is seen growing more and more irate, and one man physically puts himself between the warring pair.
The intervening passengers didn't realise they were part of a social experiment by YouTubers Trollstation, and the 'breastfeeding mum' and 'irate man' were actors.
The man who physically intervened to protect the woman looked stunned to be told he was the 'hero' of the experiment, which has shown the majority of people (at least in this Tube carriage anyway) support a mother's right to breastfeed in public and aren't afraid to speak up if need be.