Castres Olympique lead on 18 points after overpowering Dragons 42-14 on Saturday with 17 points from Julien Dumora, but the Welsh region are still in the mix for the last eight, as they are on 15 points alongside Worcester Warriors, who are second in the pool.

In Round 5, Worcester overwhelmed Enisei-STM 66-10 at Sixways Stadium, with Ollie Lawrence registering a hat-trick of tries and Noah Heward two of his side’s 10, and now play host to Castres next Friday, when Dragons entertain Enisei-STM.

In contrast, Bristol Bears, RC Toulon, Bordeaux-Bègles and Leicester Tigers are all assured of a place in the last eight after winning their pools in Round 5, with Bristol securing a home quarter-final. The other three clubs will have to wait until after next weekend’s games to find out if they have that all-important home tie in the last eight.

Pool 4 winners Bristol are the front runners with 24 match points after overwhelming Brive 52-3 at Ashton Gate on Saturday, with Callum Sheedy converting all their seven tries and kicking a penalty. The Gallagher Premiership club travel to Zebre Rugby Club next Saturday.

Pool 2 front runners Toulon are one match point behind Bristol following their four-try, 27-15 victory at nearest challengers Scarlets on Saturday, which set them up well for their home tie with TOP 14 rivals Bayonne next Saturday.

Bordeaux-Bègles and Leicester also downed their closest rivals in Round 5 but on home ground, the former beating Edinburgh Rugby 32-17 with 12 points from Matthieu Jalibert’s right boot and the latter defeating Cardiff Blues 30-20 with 15 points from their fly-half, George Ford.

Next Saturday, Pool 3 pacesetters Bordeaux-Bègles visit Wasps, while Pool 5 winners Leicester visit Pau, who are also on 15 match points after their seven-try, 47-19 success at Rugby Calvisano in Round 5.

Also in contention for the three runner-up places in the quarter-finals are Edinburgh, who have 16 points and host Agen, Scarlets (14), who travel to London Irish, Cardiff (13), who entertain Calvisano, and Zebre, who are at home to Bristol. All four games take place next Saturday.

Pool 1 promises one of the tightest finishes ever in the European Rugby Challenge Cup next weekend after it was the only group that didn’t produce a qualifier for the quarter-finals in Round 5.