Dick van Dyke..???
you wanna hear Russell Crowe do a Welsh accent in one of his
early movies back when he was a young 'un..!!

now in theory an Aussie should be able to do 'Welsh boyo'
reasonably accurately..

there is probably not much mystery why this film disapeared in recent years..
i do believe at one point he sings in a Welsh accent..

sorry cant remember the title