I read the article. If they want to keep my phone, fine. I'll claim it as lost or stolen on my travel insurance, and restore from backup. Either way, I value my privacy more than I value my phone.
As I said in the reply you originally replied to, I need it when I travel for work. Border Force aren't taking phones on the way out, but on the way in. And them taking my phone is not guaranteed to happen, whereas the inconvenience of me wiping my phone is.
The real question is why it matters to you so much what I do with my phone? Nice try Border Force...
So you claim to care about your privacy but will take absolutely no preventative measures to protect your privacy? You'll just freely hand over your phone complete with all your data, and just pray that the authorities (who are already heavily twisting and/or breaking the law here) don't falsely concoct a warrant that compels you to unlock the phone? It's very amusing that you are so paranoid about my questioning but place complete faith in the AFP.