Making sure that each of the boat's systems and emergency systems and all equipment onboard functions properly at sea when the submarine is surfaced (floating on the surface of the sea) or submerged (dived) as applicable, and to satisfy the Prime Contractor (senior company personnel acting as the customer) and the Ministry of Defence's representatives (overseers) that each system can be safely demonstrated to the Ministry of Defence (customer) and handed over to the Royal Navy (operator). Provisions must be stored onboard for these trials. Key members of the workforce (riders) accompany the naval personnel (crew) on the sea trials;
COMMISSIONING
Official Royal Navy ceremony to welcome the boat into Her Majesty's service. Traditionally, a commissioning cake is cut by the lady sponsor and the youngest member of the crew. The boat receives a pennant (flag) and a pennant number. The submarine can now carry the letters HMS before her name. This shows that she is in commission (under orders) to serve the Queen and is operating as Her Majesty's Submarine;
ACCEPTANCE AND HANDOVER
Usually carried out at sea when the Captain or Commander and the shipbuilder's representative jointly sign a document passing ownership of the submarine officially from the Prime Contractor /Shipbuilder to the Royal Navy.
