I'm just back from a long weekend in Norway, and caught a rehearsal of something to the same tune for King Harald's birthday at the Oslo Opera Theatre. According to the 'Companion to Rejoice and Sing',

"The extended words found in numerous versions.....have probably evolved ..... in much the way that football anthems have evolved on the terraces........

The origins of the tune are as obscure as those of the words. Its first official appearance was probably in Thomas Arne's arrangement made for use at Drury Lane Theatre and printed in 'The Gentleman's Magazine' for Oct. 1745, p552. ...... It was by then probably well known; Arne mentioned 'a received opinion that it was written for the Catholic Chapel of James II'.......

About twenty nations adopted the tune for patriotic songs (although in many cases they were later ousted by other settings); it is still known in the USA for Samuel F Smith's 'My country, 'tis of Thee'."