The driver was forced to intervene after tempers flared and the aggression spilled over on the number 10 bus.
Video footage has emerged that shows two passengers engaged in a heated confrontation about whether or not one of them should be wearing a face mask.
The truth is, they all should, unless there's a viable exemption. Face masks have been mandatory on all public transport in the UK since June 15.
So, during the confrontation, it seems as if a young woman was not wearing a face mask, leading to criticism from other passengers, in particular another older woman on the bus.
Other people who were present leapt in to defend her from the other woman, with the whole situation escalating until the driver became involved.
At one point, the driver tells somebody involved in the conflict to 'not lecture people about masks when you can't wear one properly'.
The person in question was wearing a mask, but didn't have it covering her nose, rendering it almost completely useless.
Seriously, as an aside, if you're going to wear the mask, make sure that it completely covers both your mouth and your nose, because otherwise you might as well not bother.
One person who witnessed the whole affair told Liverpool ECHO: "The argument was on a number ten bus going into town and it started when a young girl got on the bus not wearing a mask.
"A man and an older woman started ganging up on her and a massive row erupted.
"The bus driver had to get out of his seat and came over to demand what was going on and he told one woman she wasn't even wearing her mask properly.
"That woman then stormed off the bus and said she was going to report the incident."
People who aren't wearing face coverings and have no legitimate reason not to can be refused travel or entry onto public transport according to the rules that came into effect on June 15.
An Arriva spokesperson said: "The safety of our customers and employees continues to be our priority. The wearing of face coverings continues to be mandatory for customers whilst using public transport (exemptions apply).
"We have clear guidance and signage for customers in regards to this and all other social distancing measures in place on bus, via social media and our website for more information please visit arrivabus.co.uk."