Police have served eviction notices to travellers camped by the Jubilee River in Marsh Lane, Taplow.
The group has been given a deadline of 2pm tomorrow (Weds) to leave the fields on either side of the river.
Their vehicles began arriving on the site on Friday at about 12pm.
Sgt Stephen Bobbett, Neighbourhood Sergeant for Burnham, Taplow, Dorney and the Farnhams said there was two groups of travellers.
The first was made up of as many as 30 caravans at its peak, but had been reduced to about 15 by this afternoon (Tues).
The second group was made up of about eight caravans.
"We are working daily with land owners balancing the human rights of the travellers and the interests of the community," he said.
"We are going on to the site across the day and night as part of our assurance patrols."
He added he expected the groups to have moved on by the 2pm deadline, but warned land owners in the area to protect themselves from further problems.
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