The accent is put on but its just a thing a lot of people in London do. Like a lot of my friends dip in and out of the african accent. It's done in a jokey way but a lot of times you do it without realising.
not sure why people do it but at times done when lecturing someone, its meant to be funny like you're imitating your african elders (parents, aunties etc).
Toya did it also but heres another example of someone raised in London who does it.
also not understanding how doing an african accent is a way of getting votes but hey ho....