It's time for the final review, when suddenly some smart guy/gal has a brilliant idea: Let's involve a friend of mine who happens to be an expert in [insert specialist field here] and ask for his opinion!
Naturally, everyone thinks this is a brilliant idea. And honestly, what could possibly go wrong...
Once Pandora's box has been opened, you will find yourself having to reevaluate topics that have been shelved weeks ago. Not to mention that you will finally get the chance to tackle essential improvements, such as changing the font face, adjusting the pagination and reducing the use of the letter "m". (I once had a proposal shot down because the secretary knew someone who was a "Scandinavia expert and (!) professor"...)
Ï don't mean to knock other people's friends. We can safely assume that some of them do have a certain amount of knowledge, and they may even be proven experts in their field. BUT: This does not qualify them to jump into any work in progress on a minute's notice and overrule results that are based on detailed knowledge of a specific situation.
Unfortunately, there is no universal way to counter the ubiquitous external expert. The best way seems to be to build up your own network of advisors who can counter any specialists that might be used in an argument, e.g. "My llama expert trumps your Peruvian goat herder".