A well tube configured for use with a subsea well assembly which includes a Christmas tree arranged on top of a subterranean well. The well tube includes a bore, a lockable insert arranged within the bore, and a locking assembly. The locking assembly includes a locking dog which moves into and out of a locking position, an actuator which moves the locking dog, and a control channel which couples the actuator to an exterior of the well tube and controls the actuator to move the locking dog to removably lock the lockable insert within the bore.