keyboard battery very low notification x 400

For the past couple of days I've been getting a notification in Big Sur every minute (literally) saying that my external keyboard battery level is very low.

I haven't been using my computer for a couple of days so I've now got around 400 notifications clogging up my screen.

I can't find any way to delete them en masse, and I would rather use windows than delete each one individually.

Any ideas?