Unravel the pastry, cut off a 4cm strip along the width and chill this piece until later. Cut the remaining pastry in half lengthways. Place the pastry pieces end to end, so you have one long rectangle, squashing the cut ends together to seal. Scatter over the marzipan and orange zest, leaving a border of about 1cm free along one side. Spoon the mincemeat along the centre, like you’re making sausage rolls, then top with the apple.
Brush a little beaten egg over the exposed pastry edge. Starting from the other side, roll into a long sausage, sealing with the eggwashed edge. Use a sharp knife or a pair of scissors to snip almost all the way into the pastry at a slight angle at 5cm intervals, keeping all the pieces attached along one edge. Coil into a ring, with the cut pieces on the outside to help it bend, and tuck one end into the other to give a neat finish. Brush the wreath with egg, then use the trimmings from earlier to make decorations, such as stars or holly leaves, and brush these with egg too. Transfer to a baking sheet lined with baking parchment and chill for 30 mins.
Heat oven to 200C/180C fan/gas 6. Bake the wreath for 20 mins or until golden brown. Dust with icing sugar and serve warm for dessert, or cold as an alternative to mince pies.