The Ulster official was the referee at the centre of the controversy generated by Connacht wing Mack Hansen
Irish rugby referee Chris Busby is set for a shock retirement from professional rugby.
The Ulster official took charge of the recent interpro derby between Leinster and Connacht, after which Connacht star Mack Hansen took aim at the refereeing of his side.
According to the 42, Busby's decision is multifaceted and driven by personal reasons in the most part, although the Mack Hansen incident is believed to have been the tipping point in Busby making the decision.
Busby was due to officiate as an assistant referee for two games during the upcoming Six Nations.

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