The advice we’ve been given is that, when it comes to visiting the My Son Sanctuary, we have two choices: go in the morning when the coach parties are doing the rounds and visitor numbers are high, or risk coping with the intense heat of the afternoon when we’ll more or less have the place to ourselves. Seeing as we are one half of the “mad dogs and Englishmen” couplet we opt, of course, for the quieter, hotter alternative. As it happens, temperatures have raced up the scale since we’ve been in Hoi An and at the same time someone has adjusted the humidity setting so that T-shirts last about…