One more idea from me, possibly a juvenile/immature imperial eagle (aquila heliaca)?
I've had a good look through Collins Field Guide to the Birds of Eastern Africa and I can't find a really good match.
Juvenile Imperial Eagle is brown underneath with heavy streaking and a solid black tail.
Tawny Eagle is brown underneath and has a yellow cere.
The bird above has no coloured cere, and if you look closely at the underwing and tail you will see there is faint barring.
I'm using Stevenson & Fanshawe's Birds of East Africa and Zimmerman, Turner and Pearson's [/I]Birds of Kenya & Northern Tanzania. As Laughing Dove says, it's hard to find a really good match.
The book I am using is Birds of Southern Africa - I'll pull up the reference if you are interested - but it suggests a range of colours for Tawny Eagle including one which is light coloured underneath - but I agree about the cere.