Unless your passport shows that you've recently visited a country where there is a risk of yellow fever transmission, you won't require a certificate.
Quote:
"In accordance with International Health Regulations, a yellow fever vaccination certificate is required from travellers aged 1 year and over coming from countries with risk of yellow fever transmission"
No. I used to carry a certificate around with me but nobody anwhere ever showed the slightest interest, so I gave up. It's as Chris says, only useful if you're coming from a country with yellow fever risk.
sorry to confuse things but are you travelling back to the UK from Kenya - it was then that we got our certificates checked. Were told we would not be allowed back to the UK without it - it was checked.