The Resolution Class Submarine was a British Royal Navy Nucleur Submarine that served from 1968 to1996 before being replaced with the current Vanguard Submarine. Only four boats; the Revenge, Repulse, Resolution and Renown, were built and acted as the United Kingdoms sole Nuclear Deterrent until they were retired.
A Resolution Class Submarine acts as the launch mission for the SAS's infiltration of Murmansk. It presumably escapes before being detected by Soviet Air Patrols located it and is not seen or heard from after the player leaves the water. The Resolution Class Submarine will make an appearance in the Falklands part of the Campaign.
The Captain of the Submarine is called Henderson, it has been confirmed that this is the same character who controls the TF-141 Submarine 'Deep Control'
The letters NGER can be seen on the side of the submarine by using the out-of body glitch. Since no existing submarines had this combination of letters it is assumed that this is a fictional submarine.
The name of the boat could be Ranger. If so then it is a possible homage to a boat of the same name and class that starred in the James Bond film The Spy who Loved Me