The job was nearly done, but, like the original poster, I found it took another hour-long soak to completely clean my kettle. After that, though, my kettle looked almost as good as new.
Reddit seemed to offer a solution. In a post shared to r/CasualUK, site user u/benanderson89 said: ”[Today I learned] you can descale a kettle with a lemon.” So, I thought I’d try it to see ...