His achievements include winning gold at the British Open in 2008, 2009, 2010, 2012, and 2015. McKenzie's first foray into the European U23 Championships in 2009 resulted in a bronze medal win at Antalya. In 2010, he became the second British athlete in history to be crowned an under-23 European champion when he competed in Sarajevo. In 2011, McKenzie earned bronze and gold in the European Cup competitions within Orenburg and Hamburg, respectively. He was the 2011 Judo World Cup champion within Poland and Great Britain. He also earned bronze at the European Championships 2013 in Budapest. From 2013 to 2014, he was the back-to-back champion of the Pan-American Open in Uruguay. McKenzie would then achieve gold in the 2014 Commonwealth Games. He competed at the International Judo Federation Grand Slam 2015 in Tyumen where he won silver. McKenzie won bronze at the International Judo Federation Grand Slam 2016 in Baku.
