Complex sentence: There is a false legend saying that many decades ago, a survey of the health of students was taken, and as Hertford College's students were the heaviest, the college closed off the bridge to force them to take the stairs, giving them extra exercise.
Split into simpler sentences: There is a false legend saying that many decades ago, a survey of the health of students was taken. As Hertford College's students were the heaviest, the college closed off the bridge to force them to take the stairs, giving them extra exercise.