Police are preparing to deal with "unofficial gatherings" planned for Cambridge after the cancellation of the Strawberry Fair.
Messages from groups on the internet are calling for people to gather on Midsummer Common on 5 June.
Police challenged an alcohol licence granted to the music and arts festival first held in 1974 and organisers were forced to cancel this year's event.
Extra police will be on duty to deal with any trouble, a spokesman said.
The organisers of the official Strawberry Fair are distancing themselves from unofficial gatherings.
In a statement, Supt Mike Brown, of Cambridgeshire Police, said: "While no formal event is going ahead this year, there will be additional police officers working over the period in anticipation of likely impromptu gatherings.
"We are aware of communications between a number of groups and individuals about meeting up in place of Strawberry Fair.
"As always, public safety is of the greatest importance and if we have any concerns about this, or any offences are revealed, they will be dealt with proportionately."
Former MP's protest
The organisers of the annual Strawberry Fair called off this year's event when police challenged a liquor licence granted to them by Cambridge City Council.
Police made the challenge to question "the legal position in the licensing magistrates' court", a spokesman said at the time.
The Strawberry Fair committee said they would not have time or resources to organise the event while fighting for the licence.
David Howarth, MP for Cambridge at the time the Strawberry Fair was cancelled, said: "This is not an issue on which the police should have been allowed to dictate.
"It should be left to democratically elected councillors to make decisions like these that affect our city, not unelected police officers."