When the deployment of the Seaslug was first being considered, three classes of custom missile-firing ships were considered. The Task Force Ship would be capable of and would tasked with fleet air defence. The Ocean Convoy Escort was a vessel that would provide direct cover over seagoing convoys, while the Coastal Convoy Escort would do the same closer to shore. At that time it was believed that aircraft carriers would be able to provide adequate cover over convoys or fleets in the ocean, so attention turned to the Coastal Convoy Escort. Beginning in May 1953 a Beachy Head-class repair ship was converted into a prototype escort ship, , to test this fitting.