Formal dinners, although rare in British life, are still common in the armed forces, at some universities and in the Inns of Court. They are usually bound up in deep historical ritual and tradition and can therefore be daunting for the uninitiated.
It is the responsibility of the person who has invited you to brief you on what you should expect. If in doubt, always ask before you attend as codes of conduct and etiquette are strictly observed.
You should arrive on time and dress appropriately, following the dress code on your invitation. Look particularly to the top table for cues as to when to sit down, start eating, leave the table etc. Refrain from leaving the table during dinner. Table manners should be faultless; this really is the time to be on your best behaviour.
Be prepared for speeches and toasts. Don't finish everything in your glass and find yourself with nothing to raise a toast with. If the National Anthem is played you should be upstanding, leaving your glass on the table until the end.
If the Loyal Toast is offered simply stand and repeat 'The Queen' after the principal host. Speeches and port follow the toasts.