It was a scorching December afternoon on the Riviera Maya, and I’m not quite sure why but my partner, Charles, and I decided to walk the two miles from our hotel to the Tulum ruins. Actually, I do remember why – it was overcast and rainy the two previous days, and we needed an escape from the dreadful resort where we were staying. With the sun blazing in a cloudless sky and the pavement piping hot, we were dripping with…