Following a couple recent threads on here, I was thinking of cover versions of music that I liked. ELP's 'Jerusalem' was the first "progressive rock music" track that appealed to me as a young teenager raised on mostly crappy 'Top of The Pops' chart pop music. I didn't realise it was originally a hymn (although it isn't technically speaking a hymn, apparently) set to a poem by William Blake (my brother pointed that out to me) - I just found the overall sound and melody infinitely preferable to the pop music I'd heard before (this was years before I heard Be Bop Deluxe, etc - I was comparing it to the likes of Suzi Quatro!).
Anyway, I read that the current national anthem was recently booed at a football match, and I'd probably boo it myself - not out of any viewpoint on the monarchy/politics, but because I find the music lame and oppressive. I'd heard before that, for many people, 'Jerusalem' would be a preferred alternative. This goes back at least to King George V, who preferred 'Jerusalem' to "God Save The King".
And, of course, the official national anthem would have to be a 1970s progressive rock version, since that is what most appeals to my sense of humour! 😁👑⛪️