They didn't arrest 400 people on Cup Day this year, as happened last year in front of Parliament House. In 2020, most were arrested for gathering in a group of more than 10. However, the crowd was forced to go into a group of 400 after Victoria Police kettled them into a tight group. There was a spell when Melbourne opened back up, and police backed off protestors only to see them using more serious tactics during the most recent "snap" lockdown. https://www.youtube.com/watch?v=K5X3XSgf8Lk