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
Only handful of beaches have RNLI lifeguard cover during school holidays - the Maritime and Coastguard Agency warns.
Our Devon correspondent Seth Conway has been talking to a family who say without the hospitals, their children may not have survived.
It's going to be a windy one tonight and into the weekend - it could even touch gale force along the south coast.