For various reasons some people don't get as good an undergraduate degree result as they would have hoped (possibly as a result of health or family problems or because they enrolled for what turned out to be an inappropriate course).
The first line to take is to get reliable referees (preferrably university professors/lecturers) who can say (a) that your mathematical potential is good and (b) that you are hard working.
We may also ask you for a commitment that you will work hard on the course: we want those who come on the course to succeed! Hard work can make a lot of difference on this course.
Very occasionally we ask applicants to take an informal exam in general mathematics before we decide on whether or not to make an offer of a place.
At the end of the day we prefer to err on the side of caution: the course has a very good reputation which we wish to uphold! So we need something to tell us that you will have a successful year.
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