The UK is a has-been but you wouldn't think it from the way some trumpet their exaggerated and unrealistic views, including on AB. Actually, as you suggest (Rationalist), for decades and decades the UK got away with faking its might. In modern parlance it was a very successful PR project.
I know people in a place which never was a British possession or fought beside or against the British in any of its much vaunted wars (how wars dominate the British mindset). The British have, in the past 70 years or so, repeatedly treated that country with shameful arrogance, most recently just over a decade ago, even though the two are on paper allies and fellow founding members of NATO. On the occasion of every confrontation (UK "assault") the UK has ultimately come away as being humiliated/shamed by their own actions. Yet the people from the UK's then opponent country have repeatedly shown nothing but a spirit of reconciliation and willingness to forget only to then later receive more arrogance from the UK (the last event yet to be replaced by a repeat of the cycle - it's the UK's turn ?).
One has to wonder when, or perhaps whether, the UK can see itself realistically - perhaps once those now over 50, or is it 30, are dead ? Maybe sooner if the UK ceases to exist, but would that then be in all its constituent parts, especially the biggest one ?