Method of removing a downhole casing

Method and apparatus for removing a downhole casing from a well on a single trip. A downhole tool assembly is arranged on a work string 34 having a downhole pull tool 42, a spear tool 40, motor unit 38 and cutting device 19. The downhole tool assembly is lowered into the well, the casing is gripped by actuating the downhole pull tool and/or the spear tool, and the casing is cut. The cut casing section 18b is then pulled using the downhole pull tool to dislodge the casing section, whereupon the cut casing section can be removed from the well. The pull tool may have an anchor to grip casing 14 of a larger diameter than that being cut. The assembly can be re-set at shallower depths in the event that the cut casing section cannot be dislodged for removal. The cutting device may be actuated by the motor, which may be a hydraulic motor. The cutting device may be rotated by the motor. Also disclosed is an arrangement without a motor, wherein the pull tool has through-rotation capability to operate the cutting device.