ASo, about a month ago, I made a rich fruit cake for Christmas. Every week I have lightly fed it more brandy. When is the best time to marzipan it then cover it in fondant? (Mums request)

Depends when you want to eat it. If you want it ready for Christmas Day, I would put the fondant on on Christmas Eve. To do that, you would want to put the marzipan on 2 days before, on the 22nd. The marzipan needs to dry out a little before applying the fondant.

I'd do it anytime from now. I have already done some ready for Christmas. 

I also have mine done already.  Once the icing is on I can puddle over the decorations.

I make fruit cake every year.  I have never put marzipan on it, though I have seen many people doing it. I keep it covered tightly in foil. The longer it sits, the moister and better it begins to taste.  When I make mine I soak the fruit in juice from real oranges overnight which makes my cake very moist. I do add some of my flour to the fruit and add nuts at the time right before baking it which makes fruit evenly distribute all over cake. I have never thought about soaking it with brandy. I will have to try that one of these days!!

I do love a good fruitcake with a cup of coffee in mornings.  I have never thought about decorating a fruit cake before. I always make them every year for a few people who love fruitcake during Christmas.