Thinly pare off the orange zest using a peeler. Cut the zest into very small strips, as thin as possible. Boil the strips in a small saucepan of water for 2 minutes to remove the bitterness. Drain well and refresh the strips under cold water and put aside.
Put the juice of the orange and the lemon juice into a small pan with grated fresh ginger and Port and reduce over a medium heat for 4-5 minutes until syrupy. Strain into a clean, small pan.
Add redcurrant jelly and cranberries to the pan and warm slowly over a low heat. Add the blanched orange zest and cook for 2 minutes and stir well. Set aside and leave to go cold.