Fortunately, some students had also arrived early and were able to help me put the furniture back.
I set up my laptop, switched it on, connected it up to the screen and ... got a flickering image. This happened last year in the same room, so I knew it wasn't going to be fixed immediately. I also knew what the quick-fix remedy was.
No problem, then! Rather than use HDMI, I could use my HDMI/VGI adapter and switch to VGA.
Oh. The VGA cable had a bent pin. That wasn't going to work (and indeed it didn't).
Still now problem, though! I had the presentation on a memory stick, so could deliver it from the in-room PC.
I could, yes, except that the in-room PCs don't have the fonts I use installed and don't allow the installation of fonts. I had to switch my ppresentation to Comic Sans. Oh, the indignity....
I reported the problems with the HDMI and VGA connectors to the IT people. They're actually pretty good, so will probably fix it by next week. However, it may well get broken again by whoever it was who moved all the tables out of their way.
Sigh.