I know it’s just a joke but the “ll” in Welsh is a completely distinct character in the Welsh alphabet and doesn’t sound anything like “l”, nor is it used as a substitute for l. It’s rarely used but it has its own Middle-Welsh character: ỻ

https://en.wikipedia.org/wiki/Ll

> I know it’s just a joke

Yeah, sorry, I couldn't resist. I'm not Welsh but I lived there when I was a small child, and happily holidayed there after. It is a great country.