Ireland's John Lacey will referee marquee matches in the opening two rounds of the Champions Cup, taking charge of three time winners Toulon against defending champions Saracens at the Stade Felix Mayol on the opening weekend and then Toulouse's clash with Wasps.

On the opening weekend of the tournament, all four Irish provinces will have an English referee in charge. Leinster's game at the RDS against Castres Olympique will be presided over by Matthew Carley, Luke Pearce will take charge of Connacht against Toulouse at the Sportsground, Irish-born JP Doyle will be the man in the middle when Ulster travel to Bordeaux-Begles while Wayne Barnes will have the whistle when Munster travel to Racing 92 in Paris.

In the second round of fixtures, Munster will have France's Jerome Garces when they host the Glasgow Warriors, French newcomer Alexandre Ruiz will officiate for Ulster's game against the Exeter Chiefs, England's Pearce will be the referee when Montpellier host Leinster while Matthieu Raynal is in charge of Connacht's trip to Zebre.

Ireland's George Clancy will preside over Exeter's game against Clermont Auvergne in round one and then referee in the Challenge Cup in Round 2, a competition in which he will be joined by compatriots David Wilkinson, Dudley Phillips and Gary Conway.