This Christmas letter introduces a new character - Ilbereth, FC's Elven secretary! It would be interesting to know if there was a particular reason for his addition. Within the story it is said that a number of red and green elves have come to live with Father Christmas and help with Christmas preparations. North Polar Bear invented a system of numbers for all the children, to make present delivery more efficient. (See the bottom panel of the picture.)
However, having all the work done early precipitated (pun unintentional but too nice to remove!) the catastrophe for that year - NPB fell asleep in the bath and the water inundated the room below. That prompted his pun: "I got into hot water didn't I?"
NPB also includes a sheet with the goblin alphabet in this letter - rather complex for daily use, but interesting and typically Tolkien.
Ilbereth, by the way, has his own handwriting, firmer and more flowing than that of FC. He also has a more formal style of language.