The other day, C & I had just finished watching “The Office,” and he asked how many episodes were left. I replied “Only one” and he said “Oh no! It’s the last but one! I’m going to be so sad when it’s over.” I burst out laughing, and said “What did you say?” and he repeated, “It’s the last but one episode?”
Still laughing, I said “You can’t say it like that – you say it’s the second to last episode”. He thought about it for a minute and then insisted that it was an actual phrase, so we turned to our good friend Google. And what do you know – it is indeed acceptable to say “last but one.” Looks like English Weekend backfired on me this time!