The United Kingdom's Foreign Office states that prompt action against the Argentines prevented a more serious attack.
[3] The force, planned under heavy security, was commanded by Captain Hugh Balfour, the commanding officer of the frigate HMS Phoebe, which was accompanied by the nuclear submarine HMS Dreadnought, the frigate HMS Alacrity, and two auxiliaries, RFA Resurgent and RFA Olwen in support.
The 1977 rules of engagement were: "Commanding officers and aircraft captains are to respond to any aggression with tactful firmness and are to exhibit a determination to meet any escalation, though not to exceed that already carried out by the enemy."
The submarine commander was told: "If you are attacked with [anti-submarine] weapons by [Argentine] forces, you are to surface or withdraw at high speed submerged, whichever will be of least risk to life."
They also set up a 50-mile (80 km) security zone and any ships entering would be told that they must identify themselves and state their plans.