So the BC is in the UK?
Possibly but they could authenticate and validate the copy that Orly has, which if it is truly a certified copy, then Obambi is toast as the copy becomes a valid replacement for the original. And she will not need an original BD which would have been locally retained in Kenya.
They may also have the old ledgers, which contain the births and deaths in their archives, so the BC copy, which references a number in the Ledgers, would be clearly a real document.
Again, they may not be able to find something from so far back and from a “colony” but she may discover other things too.
Go for it Orly! And as everyonehere says and prays, be safe.