I have got this from their website:

"How to apply

You should feel free to make contact with any member of academic staff who might act as potential supervisor for your proposed research. "

From previous experience, it is NOT okay to reach out to professors before receiving an offer - so I am confused about this.
Anyone has any experience doing this successfully for Oxford Mphil or other programs?

This sounds a bit silly but what should be the structure of such an email? Talking about your own research interests and how you feel the respective faculty could help by supervising your research?? - Any tips?