Complex sentence: He was sired by Alycidon an outstanding stayer who won the Ascot Gold Cup in 1949 before becoming a very successful breeding stallion who had been the Leading sire in Great Britain & Ireland in 1955.
Split into simpler sentences: He was sired by Alycidon an outstanding stayer who won the Ascot Gold Cup in 1949. He became a very successful breeding stallion and was the Leading sire in Great Britain & Ireland in 1955.