We peered through the rain streaming down our van windows and thought, Surely he won’t attempt this. We could see down the hill to the tin roofs of Kibera, Kenya’s largest slum. And we could see mud. Lots and lots of mud. We offered to park at the top of the hill and walk down, but our guide didn’t seem to notice. So we braced ourselves as the van slid down the mucky alleys and impossible bends.