Sadly the Brits knew exactly what they were doing... A standard colonial modle was to split strong ethnic/cultural into smaller disunified colonies, where they would be a minirity in all 3-4 colonies. The borders in Africa were all done this way, with the help of the Germans, French, Portuguese and Belgians...

It made it easier to rule.

"Government at its best is a necessary evil, and at it�s worst, an intolerable one."
 Thomas Paine (from "Common Sense" 1776)