Ieuan Wyn Jones was leader of Plaid Cymru during most of the 2000's and was Deputy First Minister for Wales during the Labour-Plaid coalition (officially known as "One Wales") from 2007 to 2011.
Several years ago I was on a youth exchange in the UK, and one family had a son with this name which I found really odd. His parents had Welsh origins. Even my English host father was amazed by the spelling. I couldn't remember it properly until I found it here.
To the commenter above, this name isn't the same as Ewan, it's not even pronounced the same. Completely different name. It's pronounced "Yay Anne!" (With emphasis on the yay!)