It is really annoying when facts easily found are discarded by neophytes to Westerns.
Scott Forbes was South African, not British
The "humming" to only humming theme to a series is wrong. Those are the Ken Darby Singers who ALSO THEMED TO The Life and Legend of Wyatt Earp series and during the show of Earp until Season 4 Episode 4. And only the opening theme since. The Darby singers were used by the Desilu studios and appear in other westerns.