Fly-half Ronan O'Gara, once again, was the difference between the two sides and he finished with a personal tally of 15 points with the boot to put Munster joint top of Pool 1.

Owen Farrell, a hero for England in their victory over the All Blacks last weekend, left his kicking boots in London and missed four vital penalties which would have made a real difference for the visitors in Limerick.

Veteran Ireland playmaker O'Gara gave Munster an early 3-0 lead as the home side threw themselves at their English visitors in trademark fashion in front of a partisan Thomond Park crowd.

Munster brought their own unique brand of intense mayhem to bear on their visitors and it did spill over at times, with Saracens prop Rhys Gill and Munster's Irish international lock Donncha O'Callaghan both sin-binned during the first-half.

While both sides were down to 14-men, O'Gara slotted over a second penalty to stretch Munster's lead before centre Farrell made amends for an earlier penalty miss to claw his side back to within three points.

But Munster were six points to the good again by the break as O'Gara's ever reliable boot saw him make it 9-3 at half-time with his third penalty.

Farrell replied with his second just three minutes after the restart - 60 seconds after missing another - but O'Gara pushed the home side further ahead when he landed two more penalties to make it 15-6 after 53 minutes.

Sarries flanker Will Fraser thought he had crossed for the game's first try midway through the second half but a superb tackle by Munster wing Simon Zebo pushed him into touch at the corner flag.

Farrell was off target with two attempts after O'Gara's last effort but he did at least manage to slot over a third penalty with two minutes remaining to ensure Saracens went home with a losing bonus point ahead of the return fixture at Vicarage Road next Sunday.