Trim the base off each orange so it will sit flat, then cut off the top (keep these). Scoop out the middle, then mash through a sieve with the back of a spoon to get all the juice out. Depending on how juicy your oranges are, you may need a few extra. Put the orange shells into the freezer so they’re nice and cold.
Put the water, sugar and glucose into a pan and bring to the boil, stirring to help the sugar dissolve. Leave to cool, then add the orange and lemon juice.
Churn in an ice cream machine until smooth and creamy.
Fill the frozen oranges with the sorbet and close with the reserved tops of the oranges. Put back into the freezer for another 5 minutes or so, just to freeze the tops on.