Connacht led 8-7 at half time thanks to Tiernan O'Halloran’s score, despite being Tom Daly receiving an early red card, but O’Brien, who has scored five tries in this season’s Heineken Champions Cup, crossed for a second-half brace as Leinster ran riot.

Rory O'Loughlin’s try had kept Leinster in touch, before David Hawkshaw – who also notched four conversions – dotted down, in addition to O’Brien’s scores and further efforts from Luke McGrath, Ciaran Frawley and Max Deegan.

Elsewhere in the United Rugby Championship, Ulster Rugby, who play Stade Toulousain in the Heineken Champions Cup Round of 16, lost 23-20 at Stormers despite tries from Stewart Moore and Stuart McCloskey, and 10 points from the boot of John Cooney.

In the Gallagher Premiership on Saturday, Sale Sharks, who play Bristol Bears next month, drew 24-24 at Bath Rugby after scores from Luke James, Jean-Luc du Preez, Rohan Janse van Rensburg and Ewan Ashman

Meanwhile, tries from Antoine Frisch, Piers O'Connor and Tiff Eden couldn’t prevent Bristol going down 27-23 at Saracens.

In the TOP 14, two Heineken Champions Cup sides went head-to-head as Stade Rochelais recorded a 19-0 home win over Racing 92 thanks to four Ihaia West penalties and a late Thomas Berjon try.

In another all-Heineken Champions Cup clash, Federico Mori, Cameron Woki and Geoffrey Cros went over, with Maxime Lucu kicking 16 points, as Union Bordeaux-Bègles claimed a 31-18 win at Stade Français Paris. Lester Etien and Kylan Hamdaoui grabbed Stade Français’ tries.

Montpellier Hérault Rugby defeated EPCR Challenge Cup opposition in Biarritz Olympique, winning 37-22 at GGL Stadium as Paul Willemse (2) and Gabriel N'Gandebe notched tries and Louis Foursans-Bourdette kicked 17 points.

However, EPCR Challenge Cup side RC Toulon claimed a 32-22 win at home to ASM Clermont Auvergne - Jean-Pascal Barraque, Alivereti Raka and George Moala crossing for their Heineken Champions Cup counterparts.

Leinster Rugby wing Jimmy O'Brien went over for a try double as the four-time European champions won 45-8 at Connacht Rugby in the United Rugby Championship on Saturday, in what was a teaser of the two sides’ Heineken Champions Cup last-16 encounter next month.