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.
Here's how I show up in the court transcript from the case I was involved in last year, but unfortunately transcripts aren't generally publicly released so it doesn't seem like a simple manner of scraping
@mjg59 congrats and your affirmation!
@mjg59 Hitting the "What have they said _now_?" button.

@mjg59 Fun fact: any Christian who swears a religious oath is violating one of the clearest prohibitions Jesus Christ himself laid down for believers.

"Again, you have heard that it was said to the people long ago, 'Do not break your oath, but fulfill to the Lord the vows you have made.' But I tell you, do not swear an oath at all: either by heaven, for it is God’s throne; or by the earth, for it is his footstool; or by Jerusalem, for it is the city of the Great King. And do not swear by your head, for you cannot make even one hair white or black. All you need to say is simply 'Yes' or 'No'; anything beyond this comes from the evil one." -- Matthew 5:33-37

@Azuaron @mjg59 Indeed many people affirming would be believing Christians who are uncomfortable with the idea, not just non theists
@Azuaron @mjg59
James 5:12 says the same.
“Above all, my brothers and sisters, do not swear – not by heaven or by earth or by anything else. All you need to say is a simple ‘Yes’ or ‘No’. Otherwise you will be condemned.”