Although the in rem procedure ‘personifies’ the ship it must be remembered that the real defendant is the person who would be liable in personam as regards the claim. Thus, the in rem procedure is additional to and not instead of the in personam action. The person who would be liable in personam is the ‘relevant’ person Section 21 (4) (b), and may be the owner or the charterer by demise. The writ may only be served on the wrongdoing vessel if it belongs, at the time of arrest, to the person who is liable in personam. Thus, if that person has sold the vessel to a third party, the right of arrest is lost in respect of the vessel. To counter the harshness of the above two points the Supreme Court Act 1981 provides for the ‘alternative ship’ or ‘sister-ship’ arrest action. Only one vessel may be arrested. Although in the writ any number of vessels may be named, i.e. the ‘offending’ vessel and any alternative ships, only one may actually be arrested. This is provided for in Section 21 (8) of the 1981 Act. An example of this point is The Berny (1977). In this case the claimants had shipped sugar to Dar-es-Salaam on board ‘The Berny’, a Finnish vessel which had 18 sister-ships (i.e. 18 ships belonging to the same owner as the vessel in question). The cargo owners issued a number of writs in rem against the sister-ships of ‘The Berny’. Subsequently, they brought another action in rem against ‘The Berny’ itself and instituted an action in personam against the owners. The writ issued against ‘The Berny’ was eventually served on the vessel. The owners sought to have the service and thus the action set aside on the ground that the claimant had previously exceeded jurisdiction by issuing writs against the sister-ships of ‘The Berny’ in conjunction with issuing a writ against the vessel in question.