First contractions?

[MissBax]

Not long off my due date now, and this may sound a stupid question - but what do your first contractions actually feel like? I've been having period-y cramps on and off the last few weeks anyway, so will the first contraction feel just the same (and then increase in strength and time), or will I "know" with the first one? How debilitating are they? If I'm out in public and get the first contractions am I going to be able to drive home etc?
The main reason I ask is I've been invited to a wedding a week before due date - I have already explained I may not be there as it's so close, but if I did go and suddenly labour began am I going to be able to excuse myself and drive home (about 30 miles)?
Cheers

[Orangebird69]

My waters broke first (not textbook but not uncommon either). Contractions started about 20 mins later as a dull but uncomfortable ache at the bottom of my back. I could've driven for the first 3 hours or so but after that I'm not sure.

Tbh, I'd go to the wedding! I was at the cinema during the afternoon and out for dinner in the evening when I was 39+5. Just take your hospital bag and notes with you.