Archdruid: We come together together today to join together.... er, to accept as a fait accompli the fact that this man and this woman (or as it may be this man and this man, etc) have joined themselves together, before the legal ceremony of joining them together, on account of one of them is still legally joined to somebody else so we can't. Or something.
Living out of wedlock is an estate that we'll just have to accept on this occasion. We don't like it, but let's face it, it's an imperfect world.
Second marriages are an estate ordained of the Government and tolerated by the Church, for the giving of second chances and providing an environment in which several people's children may be nurtured. And frankly we'll all be feeling a lot more comfortable when we get them as far as the second marriage.
M and N are about to continue in their state of unwed cohabitation. They have already given consent to one another, and in token of this we'll just move on swiftly.
Archdruid: Now does anyone have any reason why this man and this woman should not be joining themselves together in holy out-of-wedlock?
Traditionalist: (from the back): How about because it's still adultery?
Archdruid: Oooh. Hadn't thought of that. I don't think we are in any place to pass judgement. Who among us could throw the first stone?
Traditionalist: Hang on - I'll nip off and get one...
Archdruid: Who giveth this woman?
P (First Husband): I will, just as soon as the decree absolute comes through. It'll be my pleasure.
Archdruid: N, do you take M to be your unlawfully appointed other half, to complain he's still down the boozer, point out that the eldest kid that causes all the trouble is his, and complain that R, his former wife, still has way too much control over him and gets too much money for the youngest one?
N: I do.
Archdruid: M, will you take N to be your equally unofficial "partner", do your best to drink the money that P sends her for their kids, and do your best to avoid being finally roped into official marriage, as long as ye both shall live?
M: I will.
Archdruid: Q, despite being the child of neither M nor N, yet you unaccountably live in their house. How do you explain it?
Q: Dunno. Did I get left over somewhere?
Archdruid: OK. I now pronounce you... man and somebody else's wife.
You may kiss... well, whoever...
Outbreak of the traditional punch-up.