The first #RailNatter holiday! (Patreon)

So... I am away for Episode 18 of #RailNatter (the week after next) and am planning to use YouTube's "Premier" feature to allow you all to have your usual chatter in the feed even though I'll have recorded the video in advance (I might join the chat remotely, mind you).

This begs the question: which theme would you like me to do a video on, bearing in mind we don't want to waste a good interactive theme on a holiday episode, but that it also needs to be interesting enough to keep us all entertained?

I was thinking of doing the "Light Rail is not a Metro" episode, but perhaps this is one you'd rather was live?