A method of operating a filter press, wherein filter material is fed into a filter chamber so as to form a filter cake between at least two sides of a flexible said filter medium. Filtrate is received from the filter chamber and the filter cake formed the filter chamber is discharged. Prior to discharging the filter cake, compression is applied on the filter cake formed within the filter chamber by providing compression fluid gas at a compression pressure exceeding a prevailing pressure within the filter chamber, directly on a side of the filter medium exterior to the filter chamber, so as to exert said compression pressure directly on said side of the filter medium, thereby causing the filter medium to yield against the filter cake.