A person who would be liable in personam may be either the owner, the charterer, or merely in possession or control of the ship. In order for that ship to be arrested, however, that person who would be liable in personam must not merely have been in possession or control of the ship but must actually have been the owner or charterer. (Of course, where the person who would be liable in personam was merely in possession or in control of the ship, although there may be no action in rem, there still could obviously be an action in personam against that person).
Of course, ‘any other ship’ may be arrested by means of the in rem procedure of which the relevant person is the beneficial owner. Thus, it can be seen that where the relevant person was merely in possession of or in control of the ‘wrongdoing’ ship (and hence that ship cannot be arrested) any other ship which is beneficially owned by that person may be arrested. It can be seen, therefore, why the expression ‘sister ship’ is something of a misnomer because in fact there need be no ownership link between the ‘wrongdoing’ ship and the ship which is in fact arrested. It is interesting to see that just prior to the bringing into effect of the Supreme Court Act 1981 it was held by the Court of Appeal, in The Span Terza (1982) that there did not have to be an ownership link between the involved ship and that selected alternatively for arrest.
It can be seen that this case almost pre-empted the about-to-be introduced the 1981 Act. It is also interesting to note that there is no requirement of this ownership link imposed by the 1952 Arrest Convention which was the basis on which Section 3 (4) of the 1956 Administration of Justice Act was formed. It is felt by some that English law in the drafting of Section 3 (4) was somewhat ‘at a tangent’ with the spirit of the Convention.