Peel the oranges and lemons with a potato peeler. Cut the peel into very fine strips.

Place the shallots in a small pan, cover with water and boil for 2 minutes. Add the strips of peel and boil for a further 2 minutes, then drain and set aside.

Cut the oranges and lemons in half, squeeze juice from the fruit and place in a small pan. Add the redcurrant jelly, heat until the jelly has melted and combined with the fruit juice, then add the mustard and port.

Mix the cornflour with the water. Pour a little of the sauce on to the cornflour, mix together, then pour the cornflour into the saucepan, stir well and gently bring to the boil, stirring until thickened. Simmer for 1 minute, then leave to cool. Keeps in the refrigerator for up to 3 weeks.