I'm Canadian. I went to Heathrow one time last year and waited in an immigration line longer than... well ever. It was around a 1 hour wait through the International line.

I don't even see a point of being part of the "Commonwealth" if there isn't a line for citizens, while EU citizens pass largely freely. Regardless of preferential treatment, I thought it was ridiculous that the EU wait time was 0 minutes (as in, there was clearly not a lineup at all) but the internationals line was incredibly long and they didn't bother adding more officers to deal with it.