La Rochelle prop Reda Wardi fails to roll away from the tackle. To be fair to him, he was underneath Tadhg Furlong. Like being trapped under a vending machine.

No matter. Penalty awarded. And Ross Byrne is going to take on the shot at the posts. Should be three...

Ross Byrne drops out long for Leinster. South African full-back Dillyn Leyds spills his catch. La Rochelle tidy up, but are under immediate pressure.

Leinster with possession and a platform, 30m out...

Leinster clack into the spring sun.

La Rochelle follow with Uini Antonio and Will Skelton looking especially frightening. Mountains of prime meat both.

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Summer sevens weather on the Atlantic coast.

An absolute carpet of a pitch.

No excuses at all for not keeping it in hand and giving it some width today...

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The two teams are playing for a Twickenham date against French league leaders Toulouse in the final of 22 May.

Toulouse edged out Bordeaux-Begles in the other semi-final yesterday with Matthis Lebel and Antoine Dupont both crossing in a 21-9 win.

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La Rochelle half-backs Tawera Kerr-Barlow and Ihaia West will start having overcome injury concerns.

Flanker Wiaan Liebenberg replaces Kevin Gourdon in the only change from the side that beat Sale in the last round.

Former Saracens second row Will Skelton is part of a formidable pack, and watch out for Fiji centre Levani Botia in midfield.

La Rochelle: Dulin; Leyds, Doumayrou, Botia, Rhule; West, Kerr-Barlow; Wardi, Bourgarit, Atonio, Sazy (capt), Skelton, Alldritt, Liebenberg, Vito.

Replacements:Bosch, Priso, Joly, Lavault, Gourdon, Retiere, Plisson, Aguillon.

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Ross Byrne will win his 100th Leinster cap as he starts in place of the injured Johnny Sexton, with Luke McGrath captains the province from scrum-half.

Second row James Ryan and centre Garry Ringrose are selected having returned from injury in last week's Rainbow Cup defeat by Munster.

James Lowe and Jordan Larmour continue on the wings having both scored tries in their quarter-final victory over Exeter.

Leinster:Keenan; Larmour, Ringrose, Henshaw, Lowe; R Byrne, McGrath (capt); Healy, R Kelleher, Furlong, Toner, Ryan, Ruddock, van der Flier, Conan.

Replacements:Tracy, E Byrne, Porter, Fardy, Baird, Osborne, Frawley, O'Loughlin.

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The players have arrived at Stade Marcel Deflandre.

And it is a real gauntlet to walk through the home fans.

Even behind closeed doors, we can't guarantee pin-drop silence over the kicking tee for Ross Byrne today.

Image source, Inpho

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O'Gara, currently head coach, will take over the top job with La Rochelle at the end of the season after director of rugby Jono Gibbes heads back to Clermont.

Gibbes is himself a Leinster old boy, spending six seasons in Dublin from 2008.

"I received an unbelievable education from Leinster. It was formative and an important part of my career, my life and I’m really grateful for that. But that doesn’t diminish my desire to beat these guys on Sunday," Gibbes said this week.

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Ronan O'Gara caught up with BBC Northern Ireland's Michael Morrow this week to talk about the philiosophy he has brought to La Rochelle.

"In France, in the past there may have not been an environment where you encouraged your front five players to pass and play with the ball," he said.

"For me that's non-negotiable, they have to be confident. But if they've been told in the past just to clean rucks and push in the scrum, I don't know how enjoyable their daily work was going to be.

"For me when I came in it was like, OK, everyone has to be able to back left-to-right and right-to-left, we've got to practise and train it."

So far, so good. As well as a first Champions Cup semi-final, La Rochelle are riding high at second in the Top 14.

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Firstly, there is this guy.

Ronan O'Gara is Munster's most decorated player, making 240 appearances on his way to becoming the province's leading points-scorer. A bona-fide red-blooded legend.

And after stints with Racing 92 and Crusaders, he is now on the latest stage of a hugely promising coaching career, bring some belief and shape to La Rochelle.

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The old hands against the new kids on the block.

That is the easy way to characterise La Rochelle - making the Champions Cup last four debut - against Leinster - who have been at this stage of the competiton 11 times previously.

But there is a lot more going on beneath that headline...