Owain Glyndŵr's revenge?

When I was a kid most signage in Wales was in English only. With enlightenment (given that all Welsh people speak English and only some speak Welsh) we moved to bilingual signs - a good thing, and a way for all visitors to acquire a smattering of Welsh words and scratch their heads over the mutated forms. Now it seems we have gone back to monolingual, on Arriva trains at least!