The accurate kicking of Chris Beaird proved decisive as Diss stretched their unbeaten run in London 1N to four matches on Saturday.
Diss were unable to cross the Luton line but Beaird was successful with four penalty kicks to see his side home.
His first penalty gave Diss the lead but the impressive visitors replied with a push-over try from a line-out to move 5-3 ahead.
Beaird's second penalty made it 6-5 at the break and two further kicks in the second half completed a hard-earned victory that pleased coach Phil Sharpe.
'We were up against a well drilled side and the boys stuck together out there and came away with a well deserved win,' he said.
'We talked a lot before the game about how we needed to take what we were showing on the training pitch into the games – and the players responded well.
'They ground out a result and gave us a platform to build on to get to where we want to be.'
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