Chas,
I asked a R/C priest about this before (a long time ago). When in the sanctuary and performing a full Mass with the Liturgy of the Word (readings) and the Liturgy of the Eucharist, a R/C priest will wear his robes (alb, stole and chasuble). When in the field, if possible, he brings a light robe (alb) and stole and dons them prior to the service. I have been to a couple of field Masses with the Scouts where all the priest had with him was a stole, which he wore over his black suit with his clerical collar (I think he forgot the alb). If he's not doing a full Mass and it's just an exchange of vows or something of that nature, he may or may not get "dressed up", whether in the santuary or the field.

By the by, our OP didn't mention which denomination he is from (or even if he's a Christian minister), just that he's the wedding officiant. Some Christian traditions here in the States don't have their ministers dress any differently from the rest of the congregation (though going to some churches these days, the pastor/celebrant may be one of the few there in a coat & tie).


Jock, as Mark said,most folks over here still consider the button-down collar to be more casual. Most of those shirts are of a coarser material (usually oxford-cloth) instead of the smoother finish of a broadcloth. However, some people consider any shirt with a collar (button-down or no) to be "formal".