In 1966 Whetton participated in the European Indoor Games taking his first major gold medal when he won the race by nearly three seconds over second placed Oleg Rayko. Whetton managed to retain the European Indoor title over the next two years, at Prague and Madrid. Whetton again represented Great Britain in the altitude influenced 1968 Summer Olympics in Mexico City, and again qualified for the final. In the final Whetton finished fifth, though a full four seconds outside the medal places. His final major medal came in the 1969 European Athletics Championships when he won the 1500 metres in Athens. In a close final Whetton beat Ireland's Francis Murphy to take the gold.