what best degree will i need to take to become a banker ?
Subject doesn't matter too much in banking, choice of university has a bigger impact.
As you go down from the target universities, the more quantitative they prefer your degree.
What degree are you interested in studying?
Whatever degree you'l do the best in. (So, on a cliche note, the subject you enjoy the most)
They'l want you to perform highly, so a high 2:1 or a first would be way more valuable than anything else.
Finance and economics generally, but the big i-banks do a lot to ensure diversity and hence are also looking for people with non-finance backgrounds such as history majors