The clip shows the mother asking the older woman to please move her bag, which was sitting on a seat reserved for less able passengers.
The seated passenger challenges the mother, saying that she hasn’t the right to sit there - even with a baby - because she doesn’t hold a first class ticket.
She adds: ‘I don’t want a screaming baby.’
To which the mother replies: ‘He's not screaming he is behaving better than you'.
A man further along the carriage asks the mother if she’d rather have his seat, which she gratefully accepts.
Other passengers can be heard applauding his gesture as the clip ends.