Poirot and his friend Hastings traveled to many places together, including Egypt. In “The Adventure of the Egyptian Tomb,” Hastings said,
The charm of Egypt had laid hold of me. Not so Poirot. Dressed precisely the same as in London, he carried a small clothes-brush in his pocket and waged an unceasing war on the dust which accumulated on his dark apparel.
I can sympathize with Poirot on this point. It is hard to give up one’s usual mode of dress, even in unusual circumstances.