Another mysterious fairy visit.

[Slick]

I had something similar last week, turned out to be a tiny hole in the tyre sidewall that was letting a small bubble of tube poke through.

You could have hit the nail on the head with that one.

A long story short, I found myself 9n a road I shouldn't have been on with almost no lights and ran over something metal resulting in a blow out. I had to replace the tyre so I assume that's an end to my troubles.