I am a South African (living in South Africa) with a British passport (Dual Nationality) I need to visit the UK in a few months time, but my British passport has expired. Can I enter the country with my South African Passport supported by my Certificate of naturalisation? Or where can I renew my Passport?
According to Timatic, you can enter Britain on an expired British passport, providing it is endorsed "British Citizen" (or some other endorsement indicating right of abode in the UK).
The idea is that all British citizens are allowed to enter Britain: they don't need permission, just proof of that status. An expired passport proves citizenship just as well as a valid one.