Cambridge MPhil supervision

I'm thinking of applying for MPhil in medical science at Cambridge and it says on the apply page I should get in touch with a supervisor before applying. I have a good proposal in mind but I was wondering how much of an input the potential supervisor will provide. Like would they revise it together with me or would they just say 'sounds good just put an application in'. And how much sway would you say the supervisor's decision to support my application will have in my acceptance?

Depends entirely on the quality of your current proposal. They won't tinker with it if it's already strong, but they may suggest you consider a different case study, methodology or whatever. The Supervisor's decision to support your application may or may not be significant. They will see lots of applications over the whole season, yours might be the best they've seen in Sept or Oct when they first see it, but it might not be the best they've seen by April.

I did get on a call with a group of potential supervisors in a "informal interview" because this course does not do interviews after application. It went really well and I've been asked to work with the post doc researcher to create a proposal together and it's looking good so far. Hopefully this helps my chances.