I only just discovered, from reading a 2014 Janet and Roy thread, that it's traditional to launch it on Chat.

[Credit to @CatThiefKeith, one of the original instigators of J&R, for the info]
So here's a link to this year's:
https://www.mumsnet.com/talk/christmas/4946911-janet-and-roy-round-robin-letters-2023?reply=130881090
For the uninitiated, here's a brief overview from @AndHarry
Janet and Roy are a couple who, back in the mists of time, sent a lengthy Christmas round robin to a MNer, who really couldn't remember who they were. This started off MNers sending round robin letters from a fictional Janet & Roy to people nominated by other posters, just for pure mischief.
How it works is posters offer to write, nominate a recipient or both. Posters make their own matches through PM, so if a poster has a nominee in mind they look for another poster who has offered to write a letter and PM them, or vice versa.
It's all in the name of good fun and to keep it in that spirit, if you have a nominee in mind please do consider whether they will find the joke funny, and you will have to tell them by the end of the year.
If you're nominating or writing, briefly say where they/you are so other posters can get a good match for location & it's not too obvious that the recipient doesn't know them when they examine the postmark for clues.
Writers, Janet & Roy can be as bland or as outrageous as you like. Last year my J&R were wealthy swingers with a penchant for all things woo :o
The more the merrier, all welcome to paticipate!