A method of unlocking a lock, the method comprising the steps of: blocking a movement of a lock member from a locked state to an unlocked state with a removeable lock core (100, 300) having a lock core body (150, 304) which is positioned in an aperture of the lock member when the lock member is in the locked state and is removed from the aperture of the lock member to transition the lock member to the unlocked state; holding a cam member tailpiece (106, 320) of the removeable lock core (100, 300) in a first cam member tailpiece position which blocks removal of the lock core body (150, 304) from the aperture of the lock member; providing an operator actuatable input supported by the removeable lock core (100, 300), an electro-mechanical drive assembly having an engaged state wherein the operator actuatable input is operatively coupled with the cam member tailpiece (106, 320) so that a rotation of the operator actuatable input causes a movement of the cam member tailpiece (106, 320) from the first cam member tailpiece position to a second cam member tailpiece position, the second cam member tailpiece position permitting removal of the lock core body (150, 304) from the aperture of the lock member and a disengaged state wherein the operator actuatable input is operatively uncoupled from the cam member tailpiece (106, 320); communicating credential information between an electronic controller of the removeable lock core (100, 300) and a portable user device; granting access to unlock the lock based on the credential information; and transitioning the electro-mechanical drive assembly from the disengaged state to the engaged state. blocking a movement of a lock member from a locked state to an unlocked state with a removeable lock core (100, 300) having a lock core body (150, 304) which is positioned in an aperture of the lock member when the lock member is in the locked state and is removed from the aperture of the lock member to transition the lock member to the unlocked state; holding a cam member tailpiece (106, 320) of the removeable lock core (100, 300) in a first cam member tailpiece position which blocks removal of the lock core body (150, 304) from the aperture of the lock member; providing an operator actuatable input supported by the removeable lock core (100, 300), an electro-mechanical drive assembly having an engaged state wherein the operator actuatable input is operatively coupled with the cam member tailpiece (106, 320) so that a rotation of the operator actuatable input causes a movement of the cam member tailpiece (106, 320) from the first cam member tailpiece position to a second cam member tailpiece position, the second cam member tailpiece position permitting removal of the lock core body (150, 304) from the aperture of the lock member and a disengaged state wherein the operator actuatable input is operatively uncoupled from the cam member tailpiece (106, 320); communicating credential information between an electronic controller of the removeable lock core (100, 300) and a portable user device; granting access to unlock the lock based on the credential information; and transitioning the electro-mechanical drive assembly from the disengaged state to the engaged state.