Ann: 2020 AGM Presentation, page-74

Shall do! But we may never know for sure.

As a long time institutional investor part of the process is to investigate scenarios where your investment thesis comes unstuck. So do it yourself, or get one of your colleagues to come up with the bear case. And there is always one out there somewhere...for every buyer there's a seller, right?
If I'm wrong what's going to cause it? Helps to ensure you're not blindsided and keeps a level of humility.

Of course you can't think of everything but constantly seeking out the short story and dismissing or incorprating it helps. IMO.