A couple faster runs in the last two days, and Strava is starting to believe in me:

Looks like it's going to be clear skies and a bit hotter than during the decent pace workouts you've logged recently. If you wake up in great form and it ends up being overcast I could see you getting in under 22 but 21 just doesn't feel possible. Best of luck

@Tarl Thanks, yeah, my target is 22:00.

I signed up for a Strava subscription, and their current performance prediction for me is a 24:05 5K.

We'll see what it looks like in a few weeks.