The joys of NuLabour - Darling get promoted for being incompetant, Mandelson gets promoted for being corrupt.

The problem with the form is that it's based on the very USA/UK way of thinking that something must either be 100% of the solution or is useless with no middle ground possible. Whereas real life(TM) tends to be more granular in nature.

Given that they where both SSBNs it seems somewhat unlikely one would be tracking the other. More likely one would track just long enough to get an idea of the other's course and speed and then head off at 90 degrees to that course.