Shacklady competed at the 1968 Summer Olympics, the 1972 Summer Olympics and the 1976 Summer Olympics. He represented England and won a silver medal in the 74kg welterweight division, at the 1974 British Commonwealth Games in Christchurch, New Zealand. Four years later he represented England again but in the 82kg division, at the 1978 Commonwealth Games in Edmonton, Alberta, Canada, finishing in fourth place.