A strong second half for the home side. Three penalties plus a try from Hudson Tonga'uiha killed the game off.
The Pirates didn't give up and pulled a late try back from Ryan Storer, but this was cancelled out by Jack Moates.
So defeat on the night and on aggregate secures London Welsh the Championship trophy.
Welsh are now expected to take legal action over the RFU's ruling that they are not eligible for promotion to the Premiership.
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Berlinah Wallace will serve a minimum of 12 years behind bars.
Mrs Justice Nicola Davies will sentence Berlinah Wallace, 48, at Bristol Crown Court.
After cool early morning weather bringing mist and fog, there should be a bright afternoon for most parts of the region.