Ronan O\'Gara booted an injury-time drop-goal after 41 phases of play to ensure a nail-biting 23-21 win for Munster over last season\'s losing finalists Northampton in the opening weekend of European Cup action on Saturday. The veteran Ireland fly-half had missed a 71st minute penalty that would have seen his team retake the lead and had to wait until the 84th minute of a frantic game to seal the result, after his forward pack had spent several minutes edging the Saints back. There was a similar story for O\'Gara\'s rival for the Ireland shirt, Jonathan Sexton, the Leinster player booting a penalty in the final seconds to help salvage a 16-16 draw for the reigning champions at debutants Montpellier. The French side were on the verge of a deserved victory until Sexton, who had missed an earlier penalty from roughly the same distance and angle, stepped up and got his side what could prove to be a crucial share of the points. His kick also prevented Leinster from emulating their team-mates two years ago when they became the first defending champions to lose their opening match of the title defence. Montpellier took the lead in the third minute as Leinster conceded a penalty, with scrum-half Benoit Paillaugue converting only for Sexton to level the match two minutes later. Sexton gave Leinster the lead with a penalty but in what was end to end running play it was the hosts who  regained the initiative. Argentinian Lucas Amorosino broke down a Leinster attack in his 22 and then hacked it clear before gathering and offloading to Fulgence Ouedraogo. The France backrow forward and club captain ran in unopposed to touch down under the posts and his try was converted by Paillaugue to send the home support wild. Leinster were rattled and captain Leo Cullen was penalised for an infringement in the line-out - Paillaugue slotted over the penalty to make it 13-6 to Montpellier. There was no let-up for the Irish province at the beginning of the second-half as Mamuka Gorgodze and Remy Martin tore holes in the Irish defence and it was only a terrific tackle by Ireland centre Gordon D\'Arcy that prevented another home try. Georgian star flanker Gorgodze was in imperious form and another of his breaks provoked another Leinster infringement, for which they were punished by France fly-half Francois Trinh-Duc who converted the penalty to make it 16-6 in the 55th minute. Leinster were making ground into the hosts\' 22 but on each occasion they failed to put their chances away and turned the ball over. Sexton blew a great opportunity to reduce the deficit with a penalty miss from almost in front of the posts but the visitors shrugged that off minutes later as Cronin touched down after being set up by D\'Arcy. The replacement hooker was brought down by Gorgodze but he got to his feet and barrelled over - Sexton made no mistake with the conversion to leave them trailing by just three points with 15 minutes remaining. Montpellier produced some sterling defence with Leinster again camped on their line, somehow holding the omni-present Cronin up on the line and then regaining possession to clear it upfield. In Saturday\'s other early matches London Irish and Edinburgh fought out a tight match with the Scottish side pulling off a 20-19 victory outscoring their opponents by two tries to one with Lee Jones and Stuart McInally touching down for them. Former champions Leicester cruised to a 28-12 victory in their away match with Italian side Aironi, scoring three tries.