Since the military build up started at Ukraine’s border in late 2021, yes (there was also a mock run at build up and invasion in 2020, that heralded the invasion in 2022). I would have thought everyone would (should) have been rather very alarmed since then, but maybe that is just me.
Consistently since 2022, Russia has threatened to sink the UK beneath the waves with nukes on tv and it’s propaganda. And the UK has consistently been the chief villain in Russian propaganda since forever.
According to international law, there is no difference if western weapons are used in strikes behind the front (inside Russia), or just in the Ukrainian territory currently occupied by Russia and the UK is in no way a participant in the war. None of us outside Ukraine is, all we have helped them with is munitions and some money. Not that any Great Power cares very much about International Law.
This changes absolutely nothing directly for the security of the UK, although if Russia’s invasion succeeds or fails; that of course has a massive consequence for the UK’s and all of Europe’s security of course. It’s just precise missiles with limited range, none can reach Moscow or threaten Russian nuclear deterrence. It does grant Ukraine some desperately needed respite in it’s valiant defence though, since it means that they can more accurately hit command HQs, logistics, airfields and munition depots in areas previously thought “safe” by Russian war command. All strictly necessary targets to hit if one is to have a snowflake’s chance in hell to stave off an invasion by a Great Power.
I mean, I am Norwegian, my government, Sweden’s government, Finland’s governemnts, all of them very much support this very loudly. And none of us have nukes like the UK does. The UK in fact has a nuclear arsenal that alone can destroy Russia. If we who actually border Russia all think this is a very wise, extremely necessary, prudent (but too late) decision and say so publically loudly so Russia can hear it; i find it a bit odd that the UK, which has nukes and many of them; should be afraid; when our governments and generals are not more fearful than “yesterday”. That having been said, we are “alarmed”, but then again, we have been so since the invasion started. Perhaps others are just a bit late in realising what started next door in February 2020.