Fun fact! UK law has not required the swearing of a religious oath under any circumstances since the Oaths Act of 1888. Before that there were various carve outs for non-Christians and other categories whose religious beliefs wouldn't allow them to swear an oath, and also exceptions for specific circumstances (such as giving evidence before a court) but since 1888 anyone has been allowed to just provide an affirmation instead. I'm kind of interested in what the proportions are.