The modern writ in rem has become a piece of legal machinery directed against the ship alleged to have been the ‘instrument of wrongdoing’ in cases where it is sought to enforce a maritime or statutory lien or in a possessory action against the ship whose possession is claimed. A judgement in rem is a judgement which is good against ‘all the world’. The in rem procedure is afforded practical effect by means of the arrest of the vessel which is the subject matter of the action. The affect of this is that just as an arrested person would be prevented from leaving the jurisdiction so an arrested vessel is likewise prevented. In strict legal theory the writ in rem and the warrant of arrest are separate legal documents but in actual practice they are invariably served on the res at the same time. Today, the procedure governing the application of the in rem procedure is found within Sections 20 – 24 of The Supreme Court Act 1981. Section 20 provides for the Admiralty jurisdiction of the High Court, and Section 20 (2) provides the circumstances which are governed by Admiralty jurisdiction. Section 21 provides for the mode of exercise of Admiralty jurisdiction. Section 2 (1) provides that an action in personam may be brought in all cases within Section 20 (2). Sub-sections 2, 3, 4 and 5 of Section 21, provide as to when an action in rem may be brought. This is in respect of nearly all the claims within Section 20 (2). Basically, it can be said that the right exists in respect of most claims for damages arising in maritime disputes. Some claims, however, are enforceable only by an action in personam: Any claim for damage received by a ship. Claims under Section 20 (3) (a). Collision actions under Section 20 (3) (b). Limitation actions under Section 20 (3) (c).