A round-up of Saturday's Investec Champions Cup action, where Northampton and Saracens got off to winning starts but Exeter were beaten by Sharks in South Africa.
Saracens powered to victory over Bulls as a 27-5 victory marked the start of their Investec Champions Cup campaign.
There was an early setback for Saracens at StoneX Stadium as the South African side's winger Sebastian de Klerk scored the opening try, but Wales prop Rhys Carre's power levelled the score and Fergus Burke's penalty gave the hosts a narrow 8-5 half-time lead.
The strong wind was to prove a decisive factor as England captain Jamie George, Tom Willis and Ben Earl all scored tries after the break.
The three-time European champions head to Stade Francais next weekend.
The Gallagher Premiership champions were out of the blocks quickly at Franklin's Gardens to lead through captain Fraser Dingwall's try, but Castres reduced the deficit with a Louis le Brun penalty as Storm Darragh made life difficult in the East Midlands.
Saints were firmly in control when Temo Mayanavanua galloped over and Tommy Freeman threw a wide pass for Juarno Augustus to make the corner, while Curtis Langdon secured the bonus point before number eight Augustus claimed a second.
Pierre Colonna touched down to give Castres some cheer but Henry Pollock rounded off an impressive Saints show with a wonderful solo finish.
Saints' next assignment is in South Africa next Saturday with a trip to the Southern Hemisphere to take on the Bulls.
The Chiefs took an early lead through Dan Frost's try while they were down to 14 - with Greg Fisilau in the sin bin, only for the Challenge Cup holders to take control for crossing over four times themselves.
Phepsi Buthelezi, Makazole Mapimpi, Grant Williams and Siya Kolisi dotted down for the Sharks, while Frost claimed a second score at the end of the first half to leave the visitors trailing 26-14 at the interval.
Kolisi's second try stretched the Sharks' lead before England winger Immanuel Feyi-Waboso claimed a crossfield kick for Exeter's third score.
Despite the Sharks being reduced to 12 men for about six minutes later with three players sent to the sin bin in quick succession, Exeter could not score a fourth try and register a bonus point.
Harlequins and Sale both lost away from home, with the London outfit going down 23-12 to Racing 92.
The French hosts seized control with 11 unanswered points in the final quarter after Alex Dombrandt and Will Porter scored tries for Harlequins and Marcus Smith added a conversion.
Glasgow scrum-half George Horne claimed a first-half hat-trick in their 38-19 victory over Sale at Scotstoun Stadium.
Kyle Rowe, Huw Jones and Scott Cummings were also on the try sheet, while Sale replied through Arron Reed, Joe Carpenter and a penalty try.
Stade played with 13 men for the final 27 minutes of their 33-7 defeat at Munster. Pierre Azagoh was sent off for catching Peter O'Mahony with a flying arm and Baptiste Pesenti saw red nine minutes later for a dangerous tackle.
Munster secured a bonus point with tries from Thaakir Abrahams, Shane Daly, Alex Kendellen and Tom Farrell.
ASM Clermont Auvergne shut out Benetton in a 28-0 victory against Stade Marcel-Michelin, with Peceli Yato and Barnabe Massa both crossing twice and Benjamin Urdapilleta converting all four tries.
Toulon overcame a 14-10 interval deficit to record an impressive 24-14 success at Stormers. Gabin Villiere, Facundo Isa and Baptiste Serin crossed for the French visitors, while Warrick Gelant and Joseph Dweba scored tries for the South African hosts.
Cardiff had to settle for a bonus point after kicking off their European Challenge Cup campaign with a thrilling 37-26 defeat in Lyon.
Matt Sherratt's side staged a strong second-half comeback as tries from Ellis Bevan and Gabriel Hamer-Webb gave them hope of clawing out an improbable win, only for the French side to respond well in the latter stages.
A swift response from Esteban Gonzalez, coupled with two penalties from Martin Meliande, ended the visitors' hopes.
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