About one hour before cooking score the skin of the duck and season, set aside.
Preheat the oven to 180c.
Make the sauce.
Finely chop the shallots. In a medium pan heat the oil and add the shallots, cook until softened. Add the grapes and cook until the fruits start to burst. Add the wine and the port and reduce by half then add the stock. Bring back to the boil and then strain through a fine sieve, reserve half the grapes and push the remainder through the sieve. Return the sauce to the pan and reduce until a syrupy consistency. Finish the sauce with the butter. Return the grapes to the sauce and keep warm.
Cook the duck breast.
Place the duck breast skin side down in a cold pan and heat until the fat renders and the skin starts to brown. Turn the duck breast over and place in the oven a cook for 8-9 minutes. Remove from the oven and rest for 5-7 minutes. Slice and serve with vegetables of your choice and the sauce on the side.