Although born in England and possibly an English national in 1900, Eric Thornton was at the time of the 1900 Paris Olympics a member of the Royal Léopold Club, Bruxelles, was studying at the University of Bruxelles, and was selected to represent them at the Games. He was a forward with Léopold FC at the time, having joined them from Uccle, but later turned to goalkeeping and in 1907 he moved to Beerschot AC. Thornton made two international appearances for Belgium, both in 1905, and both against the Netherlands. Unfortunately, he was on the end of two defeats, 1-4 and 0-4. Thornton ended his footballing career in 1911 to concentrate on his ship brokering business.