Today history will be made when two octogenarian heads of State, and leaders of their respective Churches, meet in Edinburgh.
I don't often feel glad about our Head of State also being the Head of the Church of England, but, for this one day, I can live with it. The Pope is not so keen on women having any positions of authority, so it'll be good for him to have to meet one who is his equal in every way.
I wrote last night about my mixed feelings about this visit but something else crossed my mind as I woke up this morning.
I really, really hope the Queen does not wear black. It is traditional for women to wear black when they meet the Pope to symbolise their sin while his white robes signify his purity. This is not the dress of someone meeting the Pope on equal terms, though.
I got myself in such a stew about it that I looked up on Google and the results were mixed. She certainly wore a blue dress when she met Pope John Paul 28 years ago, but there are also pictures of her dressed in black with him, a colour the ultra traditional Royal Family reserves for mourning.
I remember Princess Diana doing a nice line in mantilla chic when she went to the Vatican with Prince Charles in 1985. She looked fab, but I really found the symbolism uncomfortable, particularly when men get to wear pretty much what they want. A little bit more research told me, much to my surprise, that Michelle Obama updated that look when she met him last July.
I will admit to taking the mickey out of people's clothes in the past - ok, it's not very grown up, but we need a bit of frippery to lighten our lives from time to time. Usually, though, what someone wears is not a matter for political debate. Today, that's different.
In an hour or so we will know.