Peter Sellers: what language?

Many who saw the movie in 1962 remember only the riotous scene with uncredited (!) Peter Sellers as the Indian neurologist. He wore dark makeup, I didn't know who he was, thought he was really Indian and spoke Hindi. Years later saw the video and recognized both Sellers and the town in Wales when he said something like, "I'll have you fixed up before you can say
Llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch."