No way would I intervene in a fight involving ten people, or whatever the amount in the OP was.
Obviously call the Police though, which I presume you did. Contrary to what some people think they take this stuff very seriously in my experience.
Am I the only one who always feels slightly sorry for people who get lambasted for standing by and doing nothing?
Ten people or three people, I can’t honestly say I’m sure I’d be keen to start getting involved in random brawls in the street if I saw one.