Sounds like you should cook it really badly if you think your guest is an old git. In fact, just get a chicken - why waste duck on an old git? Why did you invite an old git round in the first place?
same way you would cook a chicken, but you need orange or a cherry sauce to go with it + usual roast potatoes & veg.I am presuming tis is a serious question and you never know the old git might bring round a bottle and be quite a nice person.