I want to secure a study leave and go to Oxford or Cambridge for a PhD in Development. I work for a Public Sector institution in Africa. I will be sponsored by my org and will return after completion. Advice me pls

Have you checked the criteria for entry into Oxbridge? I would start with that.

By another PhD, you do mean a second one?

It's a brave choice to put yourself through the stress for a second time of asking if I have read your post correctly, however, as some of us have said in the past be sure you're not denying the chance of a PhD to someone making their first attempt at one by doing so.

If you've secured sponsorship from your ORG, however, then fair enough.

Ian