with no checked bags, then yes, so long as your first flight is more or less on time. No immigration on an int-int connection, although double security at the gate for BA takes some time.

I don't think you'll have any chance if you have checked bags. Doubt if either KQ or Rwandair (guessing you're on one of those KGL-NBO) have interline agreements with BA, so you'd need to clear immigration, reclaim bags, recheck ... can't see that happening in time.