A mob of some 1,000 revellers hurled objects at officials and fuelled a massive street fire with furniture, fences and alcohol last year. Dozens were arrested and more 170 charges were laid.
This year, the city is determined things will be different.
"There should be no doubt in anyone's minds that in terms of the City of London, if you allow a party to get out of hand, it will be clear, clear, that the London Police Service will be in attendance," Police Chief Brad Duncan told The Canadian Press.
"We want Sunday to go nowhere near to the levels we experienced last year at this same time."
Authorities have spent the last two months laying out response plans for this year's festivities and will be out in full force over the weekend.
"It's the single largest deployment of individual officers on a day in most recent memory," said Duncan.
The melee last year — during which 22 police cars were damaged and a news vehicle was torched — prompted the city council to update a nuisance bylaw to boost the ability of police to deal with rowdy gatherings.
The bylaw gives officers the power to break up parties on private property with permission from the police chief or senior officer on duty.
Police have also been monitoring social media for tips on planned gatherings and have already reached out to a few individuals to warn them about the zero tolerance attitude that will be in play for any event that gets out of hand.
"That's been an important outcome for us, recognizing the impact social media can have in generating these kinds of activities," Duncan said of lessons the force has learned from last year's riot.
"We know now that there was significant movement in social media, kind of advertising the party, so we're really on top of that this year."
Police will be paying special attention this weekend to the city's downtown, the area around the University of Western Ontario and the Fleming Drive area around Fanshawe College, which was the site of last year's riot.
Authorities have also spoken with student unions about encouraging respectful festivities, a message which has resonated with the Fanshawe Student Union.
"We want to make sure that our students are aware of what the community is expecting of them," said union president Zack Dodge, who had an outreach team going door-to-door in student neighbourhoods around the college Friday afternoon to promote safe, sensible celebrations.
"We've gone above and beyond this year to make sure that London and the world around us understands that Fanshawe is a lot more than the parties and the explosions that unfortunately made their way into mainstream media last year."
Adding to the pressure for things to remain calm this weekend is the fact that London is currently hosting the World Figure Skating Championships, which close on Sunday.
Authorities have been extra vigilant and have already identified one big bash they will be monitoring closely — an event dubbed "St. Party's Day," presented by Budweiser, was scheduled to take place all day Sunday in a downtown parking lot.
Duncan said he wishes that people wake up Monday morning with a bit of a headache because they partied.
"But I don't want them waking up having to face repercussions because they became involved with the London Police Service."
— By Diana Mehta in Toronto