I've just realised I was thinking of "The Flying Kipper" (which was in Henry the Green Engine, the book right after it), and even the harbour illustration doesn't show any. I never noticed the ones behind Terence before.
So, that basically means I unknowingly made the exact guess but cited the wrong book. How did I miss those when I looked through the Wikia galleries of books 1-14? Oh, well.
So, that basically means I unknowingly made the exact guess but cited the wrong book. How did I miss those when I looked through the Wikia galleries of books 1-14? Oh, well.