Men & women of the RNXS, or Auxiliarymen as they were known (regardless of gender), were to be readily available to assist in the tasks of evacuating major ports and dispatching larger and faster merchant vessels overseas in case of an attack on the UK. Any remaining ships were to be dispersed to safe anchorages along the coasts or at nearby islands. For these purposes, the RNXS operated a small fleet of inshore vessels which were prefixed XSV for Auxiliary Service Vessel. These were mainly surplus vessels converted from other duties.
The sailing of merchantmen overseas involved setting up assembly anchorages where ships might be formed into convoys, a naval escort or surveillance for information on routing, intelligence, and communications. Auxiliarymen were required at assembly anchorage control.
These tasks were not new, indeed they had been performed by naval and merchant naval personnel throughout the past centuries. The nuclear threat, however, had cut the time available to the Royal Navy, and the Merchant Navy had to be developed or adapted to cope. Therefore the RNXS was formed.