Danny Williams (7 January 1942 -- 6 December 2005) was a British, South African-born pop singer. who earned the nickname, "Britain's Johnny Mathis", for his smooth and stylish way with a ballad. He is best known for singing his UK number 1 version of "Moon River" in 1961 and his US top ten hit, "White on White".

Based on this passage, who had a number one hit with moon river? Let's give stream of consciousness first:
The relevant sentence in the passage is: He is best known for singing his UK number 1 version of "Moon River" in 1961 and his US top ten hit, "White on White".
So, the final answer is Danny Williams.