1. Satellites and other sources indicate when a Russian sub has been deployed from their home base of Murmansk

2. Underwater sensors, located on the sea floor of the Greenland-Iceland-UK gap, will send a silent alert back to headquarters when a Russian vessel crosses into the high North Atlantic

3. Long-range patrol planes, such as the RAF's P-8 Poseidon, equipped with sensors and weapons, refines the search, perhaps aided by a friendly submarine

4. Frigates conduct an even more 'close-in' search, using towed-array sonars trailing behind the ship. The ships send out 'pings' that will hopefully reach an enemy sub and be reflected back

5. When the frigate's commanding officer is satisfied a Russian vessel has been found, they will launch the on-board Merlin helicopter to locate the submarine and, if ordered, launch a torpedo - likely a Sting Ray with 45kg of explosive charge, which is enough to punch through a sub's double hull

6. If the enemy sub remains undetected, the British sub takes up the hunt, using sonar that can detect enemy vessels up to 50 miles away.

1. Satellites and other sources indicate when a Russian sub has been deployed from their home base of Murmansk

2. Underwater sensors, located on the sea floor of the Greenland-Iceland-UK gap, will send a silent alert back to headquarters when a Russian vessel crosses into the high North Atlantic

3. Long-range patrol planes, such as the RAF's P-8 Poseidon, equipped with sensors and weapons, refines the search, perhaps aided by a friendly submarine

4. Frigates conduct an even more 'close-in' search, using towed-array sonars trailing behind the ship. The ships send out 'pings' that will hopefully reach an enemy sub and be reflected back

5. When the frigate's commanding officer is satisfied a Russian vessel has been found, they will launch the on-board Merlin helicopter to locate the submarine and, if ordered, launch a torpedo - likely a Sting Ray with 45kg of explosive charge, which is enough to punch through a sub's double hull

6. If the enemy sub remains undetected, the British sub takes up the hunt, using sonar that can detect enemy vessels up to 50 miles away.

1. Satellites and other sources indicate when a Russian sub has been deployed from their home base of Murmansk

2. Underwater sensors, located on the sea floor of the Greenland-Iceland-UK gap, will send a silent alert back to headquarters when a Russian vessel crosses into the high North Atlantic

3. Long-range patrol planes, such as the RAF's P-8 Poseidon, equipped with sensors and weapons, refines the search, perhaps aided by a friendly submarine

5. When the frigate's commanding officer is satisfied a Russian vessel has been found, they will launch the on-board Merlin helicopter to locate the submarine and, if ordered, launch a torpedo - likely a Sting Ray with 45kg of explosive charge, which is enough to punch through a sub's double hull

4. Frigates conduct an even more 'close-in' search, using towed-array sonars trailing behind the ship. The ships send out 'pings' that will hopefully reach an enemy sub and be reflected back

6. If the enemy sub remains undetected, the British sub takes up the hunt, using sonar that can detect enemy vessels up to 50 miles away.

1. Satellites and other sources indicate when a Russian sub has been deployed from their home base of Murmansk

2. Underwater sensors, located on the sea floor of the Greenland-Iceland-UK gap, will send a silent alert back to headquarters when a Russian vessel crosses into the high North Atlantic

3. Long-range patrol planes, such as the RAF's P-8 Poseidon, equipped with sensors and weapons, refines the search, perhaps aided by a friendly submarine

5. When the frigate's commanding officer is satisfied a Russian vessel has been found, they will launch the on-board Merlin helicopter to locate the submarine and, if ordered, launch a torpedo - likely a Sting Ray with 45kg of explosive charge, which is enough to punch through a sub's double hull

4. Frigates conduct an even more 'close-in' search, using towed-array sonars trailing behind the ship. The ships send out 'pings' that will hopefully reach an enemy sub and be reflected back

6. If the enemy sub remains undetected, the British sub takes up the hunt, using sonar that can detect enemy vessels up to 50 miles away.