Nairobi, June 7 -- Most men his age wake up slowly. They take morning leisurely walks, switch on the television, or sit back and let the day unfold at an easier pace.

Professor Charles Orero does none of that. At 73, he wakes up, sits at his desk, takes a fresh notebook, and begins to write, be it on a weekday or weekend.

Day after day, Orero pours his thoughts on a paper, only stopping at lunchtime, after which he comes back and writes some more until late in the evening. This has been part of his life since he retired in 2016.

In a glass cabinet inside his home library sit 180 empty biro pens.

Some are blue. Others black. A few red. All are carefully arranged, labelled, and preserved like artefacts. Each one , Orero says, represents...