That's a good point; the last few times I've flown back from Europe with Air Canada they've wanted to check passports at the gate before we got on the plane. Though I don't think I ever showed them my PR card, so a citizen with only a British passport might be OK.

I saw one guy given a thorough grilling, but I'm not sure why.

The 10 year one actually works out cheaper, plus as there is no need to actually hold a Canadian passport as I still have a valid UK one, which allows me to come and go, then I may as well wait until July 1st and apply then.

http://www.ppt.gc.ca/publications/co....aspx?lang=eng

I've boarded AC in Heathrow countless times on a British passport without a hitch. Or being asked for a PR card.

I've never been asked for a PR card by an airline and not always by the border peeps

I always ask to see a PR card if you are claiming you are a PR.
Getting back into Canada without one is not a problem, getting boarded on some airlines without one can be a problem.
Its a risk some are willing to take and I accept most travelling on a UK passport arent usually asked but there just MIGHT be that one time and it could become a costly adventure if they refuse to board you.