It looks like Kenya got permission from the start. They've been listed as a Commonwealth member since Dec. 12, 1963.
Just checked CIA Factbook. Kenya’s Constitution was amended in 1964 to . The province listed on BC,Coastal, exists as one of the seven provinces a republic. It does not give a date in 64 for the transition to republic. Whle I am unconvinced about this, it certainly seems more authentic than the Rathergate memos.