Don't know why this one aired out of order but ITVX have it as S04E16.

https://www.itv.com/watch/the-1percent-club/10a0593/10a0593a0045  

This episode has not appeared on the BBC iPlayer website because the QI XL version was removed from the schedule at the last minute and replaced with an episode from Series U.  

This episode didn't air on Tuesday January 28th 2025, it was suddenly pulled from the schedule and replaced with an episode from series U. As of this moment it is not on the BBC future schedule and the timeslot next week has a repeat of David Mitchell's Outsiders S02E01.  

When this has happened in the past it has usually been when there's something in it made distasteful by current events.  

My annual subscription was due to renew on the 26th, there was no way to add the Black Friday price so I cancelled my subscription and then immediately renewed using the half price code. I lost a week but got the 50% discount.

Apparently I've had an account since 2015 and a subscription since 2016, despite having no use for any of the premium features. I always block ads yet since I want to support the site (and selfishly not want it to run out of money and shut down) I'm happy to throw a few sheckles at a site I use daily. I even contribute data when I see an error or gap.