 Complete the following phrase:  Prieto was born in Segovia, and made his international debut at the 1983 European Athletics Junior Championships, placing fifth in the 10,000 m walk. He came seventh in the 20 km race walk at the 1985 IAAF World Race Walking Cup then went on to win a bronze medal in the event at the 1986 European Athletics Championships. He established himself as one of Spains leading walkers, competing at the World Championships in Athletics in 