@vpa2019 has given you some- but you can find them for every course offered by every college (St Andrews, oddly enough, has one of the least helpful sites in that regard). That is also why you only prepare one application, that gets sent- in it’s entirety- to everyplace you apply in the UK: your essay is about why you are a great fit for the subject you are applying to study. Oxford Hx applicants expect to reference some non-curricular reading that is relevant to area of the Hx that they are interested in for their Personal Statement (essay), and are prepared to discuss that text the interview with the History tutor who will likely teach them at some point. Dual hono(u)rs are seen as harder admits b/c tutors (profs) in both subjects have to agree that you are a good candidate.
It’s not just that you have to apply & be accepted to the degree up front, it’s that you have very constrained choices within the subject once you get there. Notice that Durham the student has 5 classes in 1st year, 1 required and the other 4 chosen from a list of ~12. At Oxford first years have 2 required classes, a choice of which Historical Methods class they want and one optional class from a list of about 20.
The UK system (tbh, most international universities) suits students who really know what they like & want to study; the US system is better for students who want a broader range of options. The collegekids have gone both ways- it really is horses for courses.