Leinster made minimal fuss in booking their place in the last 16 of the Champions Cup with a commanding 64-7 win over Bath.

The result sees the province close in on a top four finish in Pool A, which would ensure a home second leg in the next round.

It is a third defeat to end a difficult European campaign for Bath.

Leinster have racked up 30 tries and 198 points across three games to ensure their cancelled game against Montpellier, for which they were handed a 28-0 loss, did not hamper their aspirations in the competition too drastically.

Bath, chasing an unlikely last-gasp push for qualification, came out with intent and passed up several early kickable penalties in pursuit of tries as Leinster began slowly.

However, as soon as O'Brien somewhat fortuitously touched down after the ball deflected off the post in the 17th minute, there was no stopping the four-time competition winners.

On his first start since October Ireland captain Sexton delivered a fine display, dictating the tempo in his side's attack as Josh van der Flier and Jordan Larmour turned on the jets to finish flowing moves.

There was brief respite for Bath when Charlie Ewels picked off a pass and fed Max Clark for the hosts' only try before Sexton kicked in behind for O'Brien to find the bonus point score five minutes before the break, with Ciaran Frawley adding a fifth shortly after.

Bath's struggles to find a foothold in the contest were made even more difficult when Gabe Hamer-Webb was sent to the sin-bin, sparking another devastating spell from Leinster in which they scored three tries in four minutes from Andrew Porter, O'Brien and Hugo Keenan.

Despite their team's struggles the Bath crowd remained vocal throughout, and nearly had something to cheer about when Ben Spencer skipped past a tackle and looked set to collect his own chip only to be taken down by Max Deegan, with the replacement back row shown a yellow card.

With the game already won the late sin-binning had little impact on proceedings, as Leinster continued to find inventive lines of attack with Dan Sheehan charging over before O'Brien chased down a long kick into an open backfield for his fourth in the final minute.

Bath: McConnochie; Hamer-Webb, Clark, Redpath, Prydie: Bailey, B Spencer; Cordwell, Du Toit, Stuart, W Spencer, Ewels (capt), Ellis, Underhill, Bayliss.

Replacements: Doughty, Vaughan, Jonker, McNally, Williams, Simpson, Ojomoh, Butt.

Leinster: Keenan; Larmour, Ringrose, Henshaw, O'Brien; Sexton, McGrath; Porter, Kelleher, Ala'alatoa, Molony, Murphy; Doris, van der Flier, Conan.

Replacements: Sheehan, Healy, Abdaladze, Baird, Deegan, Gibson-Park, Bryne, Frawley.