The system of medical classification is intended to meet the requirements of all 3 Services. It places emphasis on such requirements as ability to march and handle weapons. For Naval purposes, physical fitness must be interpreted in terms of fitness to remain effective afloat under war conditions in any part of the world and is usually termed P2 but there are various temporary and permanent sub-categories. Categories 1, 5 and 6 are not used in the RN. Category P4 is used to denote pregnancy, P7 places temporary restrictions on medical fitness & P8 means permanently unfit to join at this time.
P0 - inpatient in hospital
P2 - fully fit for Service in any part of the world
P3 - fit for restricted service in any part of the world
P4 - pregnant
P7 - fit to serve in a restricted capacity in home, shore or harbour duties
P8 - permanently unfit Naval Service.
Suffix of P means permanent, R means temporary (eg P3P, P7R)