w > gw

Then why move it before it's sorted? It seems pointless.

Any evidence. It makes no sense for it to be anything except "Wortigern", or it would never have been remembered as Vortigern.

All Brythonic languages have the change w > gw word-initially. Therefore, this change happened in their last common ancestor, which is Proto-Brythonic by definition, before the language split into individual dialects. What evidence is there for a retention of w- in Proto-Brythonic?

I don't know.

Then gw it is.

Whatever. Just do whatever you want. I give up.