UCL exams - can I use felt-tip end pen?

Hi, a bit of a weird question.. exam regulations state blue/black ink. has anyone used a felt-tip style pen for exams?
I find rollerball pen makes my writing messy and tiring, ink pen - too straining. thin felt tip ends are fine with me, but are they allowed? I'd prefer to use them, just don't want my paper to be annulled because it's not "regulation".