If you held for 45 minutes and then diverted to Brussels, the chances are that you diverted because your fuel levels had reached the point at which you had to decide to divert. It's possible that there were lots of other aircraft waiting to land before you too. When its foggy,the extra spacing required between arrivals slows things down and hey presto 45 minutes holding. If the controller is telling the pilot it will be another 15 minutes holding, when they only have 5 minutes of holding fuel left, then you bog off elsewhere.