Real Estate / Poland - getting a tenant out (post-lease) [7]

I have a tenant who was several months in arrears on his rent. His rental contract expired several months ago, and I sent him a registered letter requesting he vacate the property. He hasn't.

I am getting conflicting advice as to whether I can call the police to get him out (in theory he is occupying my property without a valid lease) or whether I have to go through the full eviction process, which the lawyer I consulted said can last up to three years.

Has anyone had any experience with a problem such as this?