To make: Place all the ingredients except for the orange slices into a saucepan and set over a low heat. Warm through and let the juice tick over (barely simmering; certainly not boiling) for around 15 minutes. Add the orange slices and heat for 5 minutes more. Remove from the heat, strain out the bits and bobs returning the orange slices to serve if you like. If the juice is too concentrated for your taste you can add some boiling water.
Pour into heatproof mugs or glasses and drink immediately. Or, fill a flask and take to the woods.
Do you have a recipe for something delicious but non-alcoholic? I'd love to know.