I think cramming works for some subjects, depending on the nature of the course.
Subjects like Maths, or Modern History, which are really about applying knowledge and being able to use the 'facts' of the course in a sophisticated way- there is no way you'll be able to leave studying till 2 days before and do well.
But I feel that 'easier', more 'rote-learn' type subjects are able to be crammed effectively. Like Legal Studies- the course isn't conceptually difficult, and just requires memorising many facts, examples, etc. I didn't write notes for 50% of the course, and essentially learned everything about 3-5 days before the Trial, and achieved the equal highest mark. So it really doesn't work for everyone or for every course, but has potential in certain cases.