compulsary overtime is it legal

[jennie0212]

my partner works evenings to fit around our busy schedual and 4 small children his boss told him he had to do overtime forcing him to miss his day off (we always have ado some thing)on one shift and on the second shift we already had plans and the thrd shift is on a sunday when we normaly attend church (and would mean starting just 5 and a half hours after he finished the night before) So he said he coulden't do those three shifts to which she said tough you have to work these shift can she force him to work extra shifts forcing us to cancel our plans