I have been toying with a trip to YYT, I haven't been there since the 90s. Recently I had a Trip Advisor message and it discussed St Johns for a weekend break.
I was on BA sorting some other stuff and just before heading to Air Canada thought I'd try LHR-YYT on BA. I was fully expecting some error message.
To my surprise it came up with some options

LHR-YYZ BA and YYZ - YYT Westjet. Now on reflection Westjet shouldn't surprise me as they do codeshare with BA. But I wasn't expecting LHR-YYZ BA and YYZ - YYT Air Canada. Is there any BA relationship at all with AC?