This is the ballad of Sir Patrick Spens.
…and as such, really needs no introduction. A Child ballad, and one of the most famous of them.
I learned this not from Nic Jones’s version (which it resembles) but James Yorkston’s, on the 2005 mini-album Hoopoe; when I first sang it in public I hadn’t yet got hold of any of Nic Jones’s recordings. (Nor when I wrote this; the last line was an educated guess.) Seems like a while ago now.
There are many other versions (here’s one); one of these days I’ll work up the one where they try to save the ship by tying it up with string. (If you don’t want to know the result, look away now.) For now, let me tell you about where the King was, what he was drinking and what happened next.