The 2009, 2011 and 2012 European Champions were knocked out at the group stages on their way to winning the Amlin Challenge Cup last season but they are now well placed after back-to-back victories at the start of the current campaign.

Matt O'Connor's first Heineken Cup game in charge on home soil ended in a 19-7 win over the reigning French Champions, with prop Jack McGrath claiming the crucial try 21 minutes into the second half.

Jimmy Gopperth added 14 points from the tee as Leinster built on last week's fine opening win at the Ospreys.

Castres were in the contest throughout, though, with scrum-half Rory Kockott crossing for the game's first try after Gopperth had pushed Leinster 9-0 ahead inside 18 minutes.

The South African No9 darted down the blindside just past the half hour and then converted from out wide. The Castres pack was at the heart of Kockott's score, with a strong scrum allowing Antonie Claassen to pick up from the base before drawing Fergus McFadden 30 metres out.

Castres dominated the early stages of the second half after trailing by two points at the break but Leinster somehow held firm with a fierce defensive display.

Kockott could have kicked his side in front from the tee but the game turned when Castres centre Remy Lamerat saw yellow with 56 minutes played. The midfielder's shoulder charge on Dave Kearney left Castres a man short and Leinster took advantage when McGrath finished off a fine team move.

Castres initially halted a superb breakaway from inside the Leinster 22 but the hosts had the momentum and McGrath supplied the key drive after some swift recycling .

Gopperth's conversion left Castres well and truly chasing the game at 12 points down and their cause wasn't helped when replacement halfback Julien Thomas followed Lamerat to the bin with 10 minutes remaining.

Castres refused to give in, though, and they came with an inch of securing a losing bonus point as the TMO ruled that Pedrie Wannenburg hadn't quite reached the line late on.