Police moved in to make the arrests in Wellhead Park, in South Street, Bourne, after receiving calls to say a group of drunken men were swimming in the river at 10am, on Friday.

That followed reports that a group had been spotted exposing themselves outside Bourne Grammar School an hour earlier.

Police attended South Street, and arrested four men before taking them to Spalding police station for questioning.

Inspector Gary Stewart said: “Behaviour such as this will not be tolerated, as it can be extremely offensive and alarming to the community.

“The police will do everything possible to clamp down on it. I would like to send out a strong message to people to think twice before embarking on this type of activity.

“What may start out as drunken antics can quickly escalate into criminal behaviour, and lead to arrest and prosecution.

“The public has a right to expect a certain level of decent behaviour when they are out and about, and anyone who is unwilling to adhere to this will be dealt with appropriately.”