The first 40 minutes saw Stephen Myler and Nick Evans match each other from the tee, but the hosts came roaring out of the blocks after the break with North's effort six minutes into the second half breaking the deadlock to give his team a lead they would not relinquish.
Ben Botica scored a third penalty for Quins, but Dylan Hartley pounced on a loose ball eight minutes from time to score a try, and with Myler landing two superb touchline conversions in the face of a strong wind along with a penalty Saints maintained their unbeaten home record in the 2013/14 Aviva Premiership.
"Like last week it was a good team performance from one to 15," the Welshman told BT Sport. "We've been told by the coaches that we've got to share the workload. We've got a tremendous pack here and they'll work all day for us, but if we can't share that work we're not a team.
"It was one of those games where you have to keep on working for the chances to come your way, and they did today.
"We had to keep our tempo up and my try just kicked things off in the second half."
The Saints' attention now turns to the Heineken Cup. Next week sees a trip to the Ospreys, with Castres visiting Franklin's Gardens on Friday, January 17th.
It is the first time that a reigning Top 14 champion team has played a competitive game at Franklin's Gardens for many years, and it is likely that the Round 6 clash will be crucial in both clubs' Heineken Cup ambitions.
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