One duck will feed 2 people (an huge Aylesbury will do 3) as they bain`t got a lot of meat on `em, but oodles of fat.
Set oven @ 400f /gas mk 6/210c. To get a crispy skin, rub plain flour, salt & pepper on skin & dot with bits of butter. After 20 mins, lower oven to 325f/ gm3/170c. Prick the skin (but not the flesh underneath) all over & give it another 20 mins. Take it out, prick it again & give it a further 20 mins. If it`s going too brown, lightly cover with foil. I`d use Gary Rhodes recommended Crosse & Blackwell packet Madeira wine gravy for quicknes if required. So, 1 hour, plus fiddling about & 10-15 minutes to "rest" before carving. Merry Xmas.