Having previously appeared for Exeter United, Spencer Horner appeared in the first side to bear the name of Exeter City in September 1904. Playing in the first-team throughout 1904/05, he subsequently appeared for the reserves before emigrating to America.

Having previously featured for Exeter United, he made 12 appearances for City in 1904/05, and just one in 1905/06 by which time he had been appointed as captain of the reserve team.

The 1901 census records a William Spencer (as opposed to Spencer William) Horner, a nineteen-year-old Exeter-born joiner, as boarding in a house in St Sidwell’s Avenue with a family called Parkhouse. United States immigration records suggest he moved to America in 1906 and thereafter lived in Los Angeles until his death in 1974.