I am currently doing my masters in theoretical physics in Switzerland, about halfway, with most of the coursework done. I will be done with the degree by summer 2025. So far, my grades are the highest possible (6.0), and I hope to keep that up. My ultimate goal is to find a PhD dealing with gravitation, either GR, semiclassical or quantum gravity, as these topics (or what I've learned about them so far) have fascinated me most.
I started doing some research online the past few days, and have stumbled upon the Relativity and Gravitation group of the University of Cambridge, which seems to be doing exactly what I am interested in. On their website, they state that most of their PhD students come from the Part III, and the external applicants usually get positions in "less formal areas" such as lattice field theory and cosmology.
Given this information, I have started considering to do the Part III after my masters, essentially as a second masters degree, to maybe get a PhD position in Cambridge. In another post on this forum, I have read that about 10 of the 70 Part III students get PhD offers from Cambridge, and a few from Oxford. Although I am confident in my performance, I do not know how I compare internationally, so I am simply estimating a one seventh chance of getting a PhD in Cambridge after doing Part III. If I don't get one there, I would need to apply for other PhD positions in Europe.
Now comes my main question: How useful/convincing is having a Part III degree in Europe? Would this significantly increase my control over what kind of PhD I will be able to do? I am not worried too much about "losing" a year of my life to Part III, since I will finish my masters at the age of 23.
Besides answers to these questions, I would also greatly appreciate any advice on doing a PhD, either in Cambridge, Oxford or anywhere else in Europe, as I am feeling somewhat lost at the moment with what I should be doing.