Who is this following me?

It was about 27°C, but not too hot to go for a hike.
I noticed this person walking in front of me, but after a couple of kilometres he first walk side-by-side with me and then he must have been tired, because he was walking behind me. Same pace though.
The last couple of kilometres he was beside me again.

His GP must have told him to wear a hat too, like mine, to give the skin of my face some protection against nasty sun rays.