This is a reference to an American western TV series originally broadcast in the USA under the title The Adventures of Champion in the mid-1950s, and rebroadcast in the UK with a new (and better) title Champion the Wonder Horse. Champion is a wild stallion who befriends twelve year-old Ricky North (Barry Curtis) in the American Southwest in the 1880s. Ricky lives on a ranch owned by his Uncle Sandy (Jim Bannon). The boy has a penchant for getting into trouble, from which he is always rescued by Champion, with the assistance of Ricky's German shepherd dog, Rebel.
Many people believe that Frankie Laine sang the title song for the series, and indeed he did make a recording, but he was unavailable for the crucial session and his place was taken by Mike Stewart.
Here's Mike Stewart's rousing song over the intro credits to the TV show.