You don't need 4 subjects, and any 3 traditionally academic subjects (all of the ones you mention are traditionally academic) are fine. A full set of STEM subjects would also be fine for example as well (as those are also traditionally academic subjects).
Note that a) you won't specialise in "corporate law" specifically until much later and b) A-level Economics is going to be of no use because it's both going to be very out of date information by the time you get to that point in your career, and will also be so basic as to not confer any advantage over anyone else either. A-levels are not in depth academic qualifications, they just scratch the surface and provide a basic introduction to things. Compared to anyone with an undergraduate degree in a relevant area, an MBA, or actual career experience in the field before moving into law, how could A-level Economics possibly make a difference? Even assuming you remember any of it by that point to.
So don't choose a subject on that basis. Choose your subjects based on two things:
1. You think you can do well and get an A or A* in it.
2. You have a personal intellectual interest in the subject area absent any career relevance - as this will make a big difference in motivating you to actually study hard in that subject without burning out, in order to achieve 1.
Ultimately though provided you aren't taking a full set of applied/vocational subjects, universities won't really care too much about your A-level subject combination relative to e.g. your personal statement, performance in any admissions assessments like the LNAT, and if applicable interview, as well as your overall grade profile regardless of subject. As noted also your A-level subject combination would be completely irrelevant by the time you actually start working.