A method of using a downhole tool assembly in removing a casing from a well on a single trip, comprising the steps of: a) providing a downhole tool assembly on a work string , the downhole tool assembly comprising: a downhole pull tool , the downhole pull tool having an anchor mechanism and at least one piston member moveable between an extended position and a retracted position, the at least one piston member is coupled to the work string ; a spear tool ; a motor unit ; and a cutting device wherein the motor unit is configured to rotate the cutting device ; b) lowering the downhole tool assembly into the well through a first casing string wherein the casing to be removed is a second casing string located through the first casing string in the well and the spear tool , downhole pull tool and motor unit are located above the cutting device with the downhole pull tool located above the spear tool ; c) actuating the downhole pull tool to grip the first casing string ; d) actuating the motor unit to rotate the cutting device to cut the second casing string ; e) latching the spear tool to the second casing string to grip the second casing string with the spear tool ; and f) actuating the downhole pull tool to pull the work string to dislodge the cut second casing section , the downhole pull tool pulling the work string and cut second casing section upward in the well ; characterised in that : step (d) comprises actuating the cutting device by pumping a fluid into a through bore of the work string to deploy at least one knife in the cutting device ; and the downhole pull tool grips the first casing string while the motor unit rotates the cutting device to cut the second casing string . a) providing a downhole tool assembly on a work string , the downhole tool assembly comprising: a downhole pull tool , the downhole pull tool having an anchor mechanism and at least one piston member moveable between an extended position and a retracted position, the at least one piston member is coupled to the work string ; a spear tool ; a motor unit ; and a cutting device wherein the motor unit is configured to rotate the cutting device ; a downhole pull tool , the downhole pull tool having an anchor mechanism and at least one piston member moveable between an extended position and a retracted position, the at least one piston member is coupled to the work string ; a spear tool ; a motor unit ; and a cutting device wherein the motor unit is configured to rotate the cutting device ; b) lowering the downhole tool assembly into the well through a first casing string wherein the casing to be removed is a second casing string located through the first casing string in the well and the spear tool , downhole pull tool and motor unit are located above the cutting device with the downhole pull tool located above the spear tool ; c) actuating the downhole pull tool to grip the first casing string ; d) actuating the motor unit to rotate the cutting device to cut the second casing string ; e) latching the spear tool to the second casing string to grip the second casing string with the spear tool ; and f) actuating the downhole pull tool to pull the work string to dislodge the cut second casing section , the downhole pull tool pulling the work string and cut second casing section upward in the well ; characterised in that : step (d) comprises actuating the cutting device by pumping a fluid into a through bore of the work string to deploy at least one knife in the cutting device ; and the downhole pull tool grips the first casing string while the motor unit rotates the cutting device to cut the second casing string . step (d) comprises actuating the cutting device by pumping a fluid into a through bore of the work string to deploy at least one knife in the cutting device ; and the downhole pull tool grips the first casing string while the motor unit rotates the cutting device to cut the second casing string . <EOS>