This is something that you may not have thought about much, but it does happen. It’s important to establish what you’ll do if anyone turns up to your wedding who wasn’t invited.
The easiest option is to have somebody at the door of the venue – a wedding coordinator, for example – who cross-checks the name of each guest with your guest list. This stops gate-crashers from entering in the first place.
You can even hire wedding security to enforce the guest list requirement. This is a good option if you’re expecting someone particularly unwelcome to show up – such as an ex-partner whom you deliberately didn’t invite.
Which approach you take depends on what kind of uninvited guests you’re expecting. If someone decides to bring a date when they weren’t allocated a plus one, you may not even care all that much – just accommodate them as best as you can. But if you’re worried that toxic family members or former friends to crash your do, stricter measures may be necessary.
If unwanted guests are a particular concern for you, then it may be a good idea to pick ushers or a maid of honour who you’re confident can deal with them. Talk with them well in advance and make them aware that this may be part of their job description. You could even give them a list of specific people who definitely aren’t welcome, so that they know to watch out for them. Make sure they’re comfortable with the idea and fully prepared for it. Then, if the worst does happen, ensure that they know as soon as possible.
You can’t get rid of an uninvited guest unless you confront them. You can always take matters into your own hands and confront them yourself. While it would be best for somebody else to do it—you want to enjoy your big day, not talk with somebody you don’t want to talk with—you may be uniquely placed to talk to this person.
This is your final option, and it’s not a particularly pleasant one, but it may be one you’re forced to take. If you don’t have any recourse for removing this particular person from your wedding, it may be best to simply accept that they’re there and move on.
Whatever you choose, make sure you’ve decided how you’re going to handle wedding crashers long before your big day. That way, there’s no ambiguity, and your wedding party (and venue staff) know what to do if the worst happens.