Bring 1.7 litres of water to the boil in a large pan. Meanwhile, roughly chop or blitz the rosehips in a food processor.

Add the chopped hips to the boiling water, bring back to the boil, then take off the heat and leave to infuse for 15 minutes.

Pour everything through a jelly bag or a sieve lined with a double layer of fine muslin set over a bowl. Let it drip without squeezing.

Return the pulp to the pan with 800 ml fresh water, boil again, infuse for 10 minutes and strain again through the bag into the same bowl.

Now strain all the liquid a second time through a clean, fresh piece of fine muslin or a coffee filter. This removes the tiny hairs from inside the hips, which are irritating if swallowed.

Pour the strained liquid into a clean pan and boil until reduced to about 1 litre.

Add the sugar, stir until dissolved, then boil for 5 minutes.

Pour into hot, sterilised bottles and seal. Keep in the fridge and use within 4 weeks once opened, or freeze in ice cube trays for longer storage.