The best of the best.

Holders Leinster Rugby, Premiership champions Saracens and Top 14 winners Castres Olympique will be guaranteed top seedings when the pool draw for the Heineken Champions Cup takes place in Lausanne, Switzerland on Wednesday June 20.

This key event at the iconic Olympic Museum will get underway with the draw for the 2018/19 Challenge Cup pools at 2.00pm and the draw for the Heineken Champions Cup pools will follow immediately.

Both draws will be streamed live on www.epcrugby.com and on official tournament Facebook channels.

Twenty clubs from Gallagher Premiership Rugby, the Guinness PRO14 and the TOP 14 have qualified on merit for the Heineken Champions Cup. The clubs will be divided into four tiers of five and a preliminary draw will be conducted to establish Tier 1 with two of the three second-ranked clubs – Exeter Chiefs, Scarlets and Montpellier – joining Heineken Champions Cup and PRO14 winners, Leinster, Premiership winners, Saracens, and TOP 14 winners, Castres, in the top tier.

Once Tier 1 has been established, the remaining three tiers will fall into place. Tier 2 will include the three third-ranked clubs from the leagues – Wasps, Glasgow Warriors and Racing 92 – as well as the second-ranked club which was not drawn into Tier 1 and the fourth-ranked club from the same league as the club which was not drawn into Tier 1.

Tier 3 will include the two clubs ranked fourth which are not in Tier 2 as well as the three fifth-ranked clubs from each league – Leicester Tigers, Edinburgh Rugby and Toulouse.

Tier 4 is complete and contains the sixth-ranked clubs from each league – Bath Rugby, Challenge Cup winners, Cardiff Blues, and RC Toulon – as well as Ulster Rugby and Gloucester Rugby.

When the tiers are completed, the main draw for the five pools will be made, and during the draw, some clubs may have to be placed directly into a pool in order to ensure that the key principles apply.