The claimant who holds a maritime lien may effect the lien by bringing an action in rem against the ship. This is procedurally governed by Section 21 (3) of the Supreme Court Act 1981. This Act set out the situations in which a ship may be arrested by the in rem procedure. It should be noted that the fundamental difference between the rights in rem as granted by statute and the general right of arrest in respect of a maritime lien. The latter is not created by statute but merely procedurally governed by the 1981 Act. The difference of course lies in the fact that the maritime lien (and the consequent right over the res) arises as soon as the incident which creates the lien occurs. Thus, it does not matter if the res is sold. The statutory right in rem is said to occur when the action is taken, i.e. by the issuing and serving of the writ. The statutory right of arrest does not, therefore, come into being until this point i.e. not at the moment when the incident arises (as with the maritime lien) but only when the writ is actually served. Thus, the statutory rights in rem will be lost if the vessel is sold.