I've been banned from my stag do

If your best man has organised the whole trip already then it would be a shame to let him down at the last minute. Planning a stag party takes quite a lot of time and effort so telling him that you, the groom, can’t attend would probably be inappropriate and disappointing. Maybe speak to your fiancée and try and find out the reasons why she doesn’t want you to attend your own stag party. Is she worried about what you will all be getting up to? Maybe you could draw up some guidelines together before you go to put her mind at ease.