

At present? Keeping an eye on Russian ships “just out for a walk” so to speak, in waters nowhere near their immediate interests that happen to be a lot closer to British interests.
Why does that need to be a jet? To remind those ships that if they were to bring their own jets for whatever reason, not that they’d ever even have the remotest possibility of the merest inkling of a thought to do such a thing, we’d be prepared.
Mild sabre rattling. Also known as “international diplomacy”.
My first thought was that this was arranging to put fish in a barrel, to allude to a certain metaphor, but then I realised that it was more likely the other way around and it’s a concentration camp, and your comment was already here.
And then I remembered how camps usually go and that it would be both at the same time.