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.
More top news
She may not look like she's had a near-death experience but Aunt Bessie is "Staying Alive" thanks to that song by the Bee Gees.
Residents living near the Somerset Levels are positive the dredging of 150,000 cubic metres will prevent any serious flooding
A woman has been charged over an alleged scam, in which it's claimed people lost money on holidays in Rhyl and Devon that didn't exist.