One of these reminds me of an old tradition... if the groom does not shwo up, the best man has to marry the bride. This is from the days when the best man was usually the groom's brother or nearest male relative and there was a contract or alliance between houses which was secured by the marriage. If the groom cannot marry her, someone else in the same family has to.

There is also a tradition that the best man carried a sword into the ceremony in case any of the Bride's other suitors decided to try to kidnap her. The best man was expected to help the groom defend her honour.

Another one I have heard which I am not sure is true or not (or where/when it comes from) is that the stag night was originally the Bride's family kidnapping the groom to make sure that he could not run away the night before - keeping him well fed and too drunk to escape. With this in mind, you could arrange to kidnap the bride the night before and keep her locked up lest she try to escape

Though be careful about this sort of thing... registrars (in this country at least. not sure about elsewhere...) are always aware of potential forced marriages which is why they can, by law, insist on interviewing both the bride and the groom seperately and away from parents and other possible influences. If they think there is any element of cohersion they will not perform the marriage and will also arrange a safe place for the bride (or groom, I suppose). So, assuming this is the case where you are, you need to either make sure that the registrar knows what is going on and why or that nothing happens that he/she can see which would cause concern.