Lol, unless you want to work in law, medecine, engineering, research, technical consultancy, or any one of a massive number of careers in the city. Not to mention any kind of management.
Not entirely true actually
Unless you want to be a slave at an investment bank on one of their graduate recruitment programs - spend 2 years working your ass of 14 hours a day & no guarantee of a front office position at the end of it anyway - no thanks tbh....
There are several hundred thousand people working in the city and only a fraction of them had to go through that milk round bollocks. Brokers need to have good interpersonal skills and traders need to be disciplined and analytical neither actually *need* to have degrees.
Plenty of doors can be opened in the city by simply getting your FSA exams under your belt. Having said that it is no disadvantage actually having a degree and (though not essential) it still preferable to not having one.
In terms of the general subject of the thread whether or not youve got a degree is dependent on the career you intend to pursue.